Clear skies over these next few nights and enough personal stamina to stay awake will afford a view of one of the flashiest meteor displays of the year. The annual Perseid Meteor Shower has been slowly ramping up in intensity since this past weekend and viewers from around the world have been delighted by views of these bright streaks of light darting across the night sky. In some special cases, they’ve put on spectacular—albeit brief—shows.

On Saturday, Ernõ Berkó from Ludányhalaszi, Hungary witnessed a Perseid that he estimated at magnitude -10; more than one-hundred times brighter than the planet Venus (which, along with Mars and Saturn currently adorns the southwest sky right after sunset).

Excellent New England weather last weekend brought more than a thousand amateur astronomers to the 75th Stellafane Convention, just outside of Springfield, Vermont. While the emphasis was on observing the sky with telescopes, many participants also enjoyed the views of an occasional Perseid cutting a path across the sky. Every time one was seen, the watchers said: “Ooooohh!” Steve Lieber of the Astronomical Society of Long Island (ASLI) notes: “On Saturday night, one bolide (exploding meteor) lit up the field. Looked like a flash going off. Saw the vapor trail for 15-20 seconds after that.” And the best is yet to come!

The peak of this year's Perseids is forecast (for North America) to come during the afternoon hours on Thursday (Aug. 12), which means that greatest number of meteors will probably be seen late that night into the predawn hours of Friday. At these times a single observer might count anywhere from 60 to 100 per hour.

But don’t overlook late Wednesday night (Aug. 11) into early Thursday morning, when about two-thirds of that number might be seen. And even late on Friday night (Aug. 13) into early Saturday hourly rates will still be respectable, though probably numbering about one-quarter to one-half of the numbers seen on the peak night. Over this upcoming weekend you can still probably catch sight of a lingering few.

Comet Crumbs

The Perseids are the remnants of Comet Swift-Tuttle, which last visited the inner solar system in 1992. Every August, like clockwork, our planet Earth cuts through the “river of rubble” left behind along the orbit of the comet. And yet, while comets are composed chiefly of frozen gas, meteors are very flimsy. They’re material that has flaked off comets and they’re similar in consistency to cigar ash; they litter up our solar system. Most are scarcely larger than pebbles or sand grains. In the case of the Perseids, they come crashing into Earth’s atmosphere at estimated speeds as high as 37 miles per second—133,000 miles per hour. These tiny visitors from the cold, vast voids of stellar space, have been orbiting in the solar system for perhaps hundreds or even thousands of years, but cannot survive the shock of entry, and end up streaking across the sky in a brief, blazing finale lasting but a few seconds. Their kinectic energy is used up in such processes as the production of light, heat and ionization. Thus, such a tiny particle bursts into incandescence from friction, producing the shooting star effect and can be seen from more than 100-miles away.

But it’s really the light energy it develops, not the particle itself that we see.

Observing Tips

Astronomers offer this advice: Get as far away from bright city lights as you can, although a few of the brightest meteors may be glimpsed even over the sooty curtain of large, light polluted metropolitan areas. Hope for a clear, dry night. You can start your watch as early as 10 p.m., although the best views will come between 2 a.m. and the first light of dawn. Any lawn or rooftop can serve as an observatory when it comes to meteor watching. Relax in a lawn chair and scan the heavens from the south over toward the northeast. They are named the Perseid meteors because their fiery trails, if extended to a common point of intersection, would seem to originate near to the Double Star Cluster in the constellation Perseus , which on mid August evenings rises from the northeast.

But their associated meteors could make their fiery plunges into the atmosphere over a wide range of the sky. As the night progresses, the stars of Perseus, which lies low to the northeast horizon before midnight, will slowly climb progressively higher into the sky. During the first part of the night, the meteors may appear to describe rather long paths across the heavens; after midnight they’ll appear more like short, swift streaks. As has already been noted, some Perseids leave particularly long-enduring trains in their wake. With binoculars one can see these trains drifting against the backdrop of the stars, indicative of swift winds in the very high atmosphere. But generally speaking, binoculars and especially telescopes are not particularly recommended because your unaided eyes can take in much larger areas of the sky.

And there is absolutely no danger in getting hit by a Perseid because they are consumed high above our heads at altitudes of 60 to 80 miles. One former Chief Astronomer at the Hayden Planetarium, the late Dr. Kenneth L. Franklin, often would point out that the only dangers from watching a Perseid shower is getting drenched in dew and falling asleep.

For those who sleep through the Perseids, the next really prominent meteor shower will come in mid-December, the time of the Geminid Meteors.

Early next Monday morning (April 5) at 6:21:22 a.m. Eastern Time, the Space Shuttle Discovery is scheduled to be launched on mission STS-131 to the International Space Station. If the flight comes off on time, it will take place 46-minutes before sunrise at the launch site at Cape Canaveral, Florida. Along much of the United States Eastern Seaboard, it will be morning twilight . . . a most unusual circumstance for the launch of space shuttle. Only five out of the 130 previous shuttle flights have taken place just before sunrise on Florida's "Space Coast" and this will be the very first morning twilight launch to take a northeast trajectory parallel the East Coast.

The question one might ask at this point is, "Will Shuttle Discovery be visible locally from the Greater New York Area soon after it leaves Pad 39A in Florida?" To answer this question, I revisited a similar shuttle launch which took place back in 1991.

On September 12 of that year, shuttle Discovery was launched on mission STS-48, in order to place UARS (Upper Atmospheric Research Satellite) into orbit. Liftoff came at 7:11 p.m. Eastern Time. In Florida this was 20-minutes before sunset, while it was exactly the moment of sunset in New York. Eight minutes later, the shuttle came up over the southern horizon as seen from here in the Metropolitan Area. It streaked rapidly on a relatively low trajectory above the horizon, appearing to equal or even rival the planet Venus in brightness. At the moment of MECO (Main Engine Cut Off), ground observers could see a "puff" of vapor emanating from the shuttle and immediately afterward, looking at the shuttle with binoculars revealed two objects: the shuttle orbiter and the orange external fuel tank which had just been jettisoned over the Atlantic. It only lasted about a minute, but it was all very exciting to watch.

Now . . . we may have another chance to see something similar in our early morning sky next Monday.

The 1991 shuttle launch was during the evening hours. When the shuttle appeared over New York it was eight minutes after local sunset and the Sun was 1.7-degrees below the horizon.

On Monday morning, assuming an on-time liftoff at 6:21:22 a.m., prospective shuttle watchers should start to concentrate on the south-southeast horizon at 6:28:30 a.m. EDT. The Sun will be 2.3-degrees below the horizon, so twilight conditions will be quite similar to September 1991. Sunrise will come about five minutes later.

Shuttle Discovery will appear to rapidly streak eastward, and will appear about 7.5-degrees above the southeast horizon at the scheduled moment of MECO (6:29:43 a.m.). I expect Discovery to appear between magnitude -2 to -4 or somewhere between the brightness of the planets Jupiter and Venus. Since the amount of reflected sunlight will be diminishing as the shuttle races across the sky toward the east, it might appear to rapidly fade from view around the time of MECO. While the shuttle should initially be readily visible to the unaided eye, binoculars will certainly aid in keeping the shuttle in view for a longer interval of time.

Good Luck and clear skies!

With the Space Shuttle Endeavour scheduled to undock from the International Space Station (ISS) on Friday evening, skywatchers across much of the United States and southern Canada are in for a real treat early on Saturday and Sunday morning.

Weather permitting on these mornings, there will be opportunities to see both the Endeavour orbiter and the ISS flying across the sky from many locations.

Appearing as a pair of very bright "stars," the ISS should appear as a somewhat brighter object and will be trailing Endeavour as they move across the sky. The pair will appear only a few degrees apart on Saturday morning, but the gap between the two will likely widen to perhaps 20-degrees or more by Sunday morning (your clenched fist held at arm's length measures roughly 10-degrees; so on Sunday morning expect Endeavour and the ISS to separated by about two fist-lengths).

The sight should easily be visible to anyone, even from brightly lit cities. Considering that after this mission there will be only be four left before the shuttle program ends (tentatively in September) the view of a shuttle orbiter and the Space Station flying in tandem will soon be a sight that will pass into history.

New York's View

The Tri-State Area will get two opportunities to see Endeavour flying with the ISS. The first will come on Saturday morning, just over 9 and a half hours after both vehicles have undocked; so they will still be relatively close to each other. The two spacecraft will emerge from out of the Earth's shadow at 5:21 a.m. EST, at an altitude of 18-degrees above the north-northwest horizon. They will attain a maximum altitude of 25-degrees above the north-northeast horizon at 5:23 a.m. and will drop toward the eastern horizon at 5:25 a.m. If you're familiar with the constellations, you'll see them glide between Cepheus and the "W" of Cassiopeia and pass under the bright star Deneb in Cygnus. Overall, this pass should last about 3 minutes and 50 seconds.

Your other opportunity will come early on Sunday. By then, the two spacecraft will be more widely separated (recall the "two fists" rule), but they will trace a much higher arc across the sky. Emerging from the Earth's shadow, about 15-degrees above the northwest horizon at 5:43 a.m. EST, Endeavour and the ISS will climb to a maximum altitude of 63-degrees above the northeast horizon at 5:45 a.m, then drop down toward the east-southeast horizon by 5:48. Overall, this pass should last 5 minutes 10 seconds! At their closest point (when highest in the sky), they should be about 240 miles away. If you're familiar with the constellations, they will appear to pass between the Big Dipper and Polaris (the North Star), then streak past the lozenge-shaped head of Draco, then, as they descend they will pass close to two of the brightest stars in the sky: Vega in Lyra and Altair in Aquila. Interestingly, the ground track for both vehicles shows that they will appear to pass directly overhead (or very nearly so) as seen from Catskill, NY in Columbia County.

Region of visibility

Generally speaking, the tandem will be visible across southern Canada and most of the 48 contiguous United States (Hawaii and Alaska will not have favorable viewing passes during this upcoming week).

Across southern Canada and the northern half of the United States there will be two or three morning viewing opportunities. For some favored locations, like Chicago and Milwaukee there will be as many as four opportunities. Over the southern United States, the viewing opportunities will be reduced to just one. Much of Florida (save for the Panhandle), central and southern Georgia, and parts of western and southern Texas will unfortunately be denied a view of the "dynamic duo" because they'll appear too low in the sky and too near to sunrise to be easily visible.

For other locations . . .

So what is the viewing schedule for your particular hometown? You can easily find out by visiting one of these three web sites:

• Chris Peat's Heavens Above
• NASA's SkyWatch
• Spaceweather.com

Each will ask for your zip code or city, and respond with a list of suggested spotting times. Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they can change due to the slow decay of the space station's orbit and periodic reboosts to higher altitudes. Check frequently for updates.

Another great site is Real Time Satellite Tracking, which shows where the ISS or Space Shuttle are at any given moment during the day or night.

What to expect

Both vehicles will be traveling across North America on northwest-to-southeast trajectories.

A large telescope is needed to make out details of the sprawling station. Traveling in their respective orbits at approximately 18,000 mph (29,000 kph), both should be visible anywhere from about one to five minutes (depending on the particular viewing pass) as they glide with a steady speed across the sky.

Because of its size and configuration of highly reflective solar panels, the space station is now, by far, the brightest man-made object currently in orbit around the Earth.

On favorable passes, it approaches magnitude -5 in brightness, which would rival the planet Venus and is more than 25 times brighter than Sirius, the brightest star in the night sky. Some have even caught a glimpse of the ISS just prior to sunset or shortly after sunrise. And as a bonus, sunlight glinting directly off the solar panels can sometimes make the ISS appear to briefly flare in brilliance.

Other satellites too

The appearance of either the space shuttle or the space station moving across the sky is not in itself unusual. On any clear evening within a couple of hours of local sunset and with no optical aid, you can usually spot several orbiting Earth satellites creeping across the sky like moving stars. Satellites become visible only when they are in sunlight and the observer is in deep twilight or darkness. This usually means shortly after dusk or before dawn.

What makes the prospective upcoming passages so interesting is that you'll be able to see the two largest orbiting space vehicles in the sky at the same time.

Shuttle Endeavour is expected to undock from the ISS at 7:54 p.m. Eastern Standard Time on Friday. Endeavour will fly around the ISS before finally pulling away from the Station at 9:38 p.m. EST, although it should still remain at a relatively close distance to it until its scheduled return to the Kennedy Space Center in Florida Sunday evening.