Post by rufffan on Aug 26, 2003 19:25:58 GMT -5
THE SPAN of space is small only in the cosmic sense, however. Despite rumors, there will be no chance of collision and no unusual or dangerous gravitational effects. It is just a wonderful opportunity for anyone to enjoy a slice of astronomical history and to see Mars as bright as it can be.
Public interest in the event has soared recently as media around the world cover the story, which was first reported by Space.com last November.
“It’s taken on almost a mystical importance with people,” said Ray Villard, news director at the Space Telescope Science Institute, which operates the Hubble Space Telescope.
Hubble, which orbits Earth, will take advantage of the proximity by snapping two pictures of Mars for release Wednesday. The first will be available shortly after 6 a.m. ET.
WHERE TO LOOK
Click through 20 years of the "greatest hits" from the Red Planet.
Mars rises in the southeast around sunset, your local time, shimmering like an orange star so bright it could momentarily be mistaken for an airliner on final approach. It outshines all other stars in the sky. Around 1 a.m. Mars is due south and high in the sky. It sets in the southwest at about sunrise.
No equipment is necessary to observe Mars closer than has any human in the past 59,619 years. But the best views are afforded through telescopes, which can reveal surface markings, the south polar ice cap and clouds. For this purpose, astronomers recommend at least a 70mm lens for so-called refractor telescopes, or 4.25 inches for the reflector type.
However, telescopes are in short supply at many stores, as a sort of Mars mania has folks scurrying to buy optical aids.
People in many communities will flock to local observatories and amateur astronomy outings for a chance to peek through really big telescopes. Web searches can yield contact information for local astronomy clubs, and the Planetary Society has created an extensive list of related events.
A complete Mars Viewer’s Guide is available from Space.com.
DON’T WORRY IF YOU MISS THE MOMENT
Everyone has potential ringside seats to this celestial wonder. Mars is visible to anyone on Earth with clear skies. And the exact instant of the closest approach is relatively unimportant, other than marking a curious mathematical moment.
In fact, many people will not see Mars at 5:51 a.m. ET Wednesday. It will have sunk nearly to the southwestern horizon for residents of eastern North America, and it will be broad daylight then in Europe and other parts of the world. Weather could ruin the view for some hopeful observers.
Mars, though, is essentially the same brightness any night or early morning now through Sept. 2, and it will remain a delightful skywatcher’s target into October.
The unusually close approach — less than 1 percent closer than a similar event in 1971 — is created by a confluence of orbital oddities.
Earth and Mars are like cars on a racetrack, with Earth on the inside. Every 26 months or so, Mars is at opposition — directly opposite the sun in relation to Earth, just as Earth “laps” Mars in the never-ending race. Mars reaches opposition this week, causing it to rise around sunset and set at sunrise.
As with any opposition of Mars, this one offers a shorter path for spacecraft, and four of them are bound for the Red Planet right now. NASA has two probes en route, slated to land and deploy rovers in January. Another lander was shot to Mars by the European Space Agency, and the Japanese have a Mars orbiter on the way.
WHAT MAKES THIS ONE SPECIAL
For skywatchers, this opposition is particularly special.
The orbits of both planets are not quite circles. So every 15 years, a Mars opposition comes when the Red Planet is about as near to the sun as its orbit ever carries it (a point called perihelion) and Earth is near its outermost point (called aphelion).
Further, the two orbits actually rotate in space, bringing Earth’s aphelion and Mars’ perihelion to even greater proximity at certain times — like this week.
Imagine each orbit being shaped a bit like the outline of a football (the oblong, American variety). A smaller football is rotating freely inside a larger one. Every now and then — as measured in cosmic time — the pointy end of the inner football is lined up with the laces of the outer football.
With all these factors involved, the timing of the closest approach rarely if ever coincides with the moment of opposition, but they’re usually within a few days of each other. Mars achieves opposition the day after this year’s close approach.
As of Tuesday, this serves as the sharpest image of Mars ever taken by the Hubble Space Telescope. Hubble scientists say a fresh, even sharper picture will be posted to the HubbleSite shortly after 6 a.m. ET Wednesday.
There is yet another factor at work.
“Mars has been slowly getting closer to the sun at the perihelion point of its orbit (that part of the orbit closest to the sun),” explains Joe Rao, Space.com’s Night Sky columnist.
Rao, who has been scrutinizing this year’s close approach since last year, says this change in Mars’ orbit has probably contributed to a bunching of similar events over the past few centuries.
In fact, an even closer pass is on the horizon, at least for a future generation of skywatchers. In 2287, Mars will be slightly nearer to Earth than it is this week.
