The story of my electric bill will be continued in the next posting.
This is about a comet. The math has to do with exponents and powers. If you haven't yet learned about exponents and powers (you will), ask a teacher or post a comment. Part of a news story follows:
In terms of actual measured brightness, 17P has moved from a magnitude of 17, which is visible only through a large telescope, to somewhere just above magnitude 2. That's an increase of about 1 million times, Herbst said, and it makes the comet visible to the naked eye even in urban settings where the night sky is obscured by man-made light.If B is brightness and M is magnitude, B = (base)^-M ; B is (base) to the minus M power. The number (base) is defined by (base)^5 = 100. The number (base) is about 2.511. Since the magnitude changed from 17 to about 2, a change of about 15, and 15/5 = 3, the brightness increased by 100 cubed, or 100 x 100 x 100, or about 1 million. All the "abouts" in the last sentence are because different observers have made different estimates of the brightness now. They think it is about 2nd magnitude; they are comparing it to other stars. Stars of first magnitude are bright, stars of 2nd magnitude less bright, stars of 3rd magnitude still less bright, and so on.
The comet was first seen on November 6 1892. It comes near Earth every 6.88 years. When did it last come near Earth (and nobody payed attention since it was 17th magnitude)? When will it next come near Earth?
This is the whole news story:
dailypress.com/news/dp-news_cometholmes_1105nov05,0,5662681.story?coll=dp-wid
dailypress.com
Stargazers aglow over comet's stunning visit
A usually dull passer-by named Holmes has local astronomers staying up late to get a celestial eyeful.
By MARK ST. JOHN ERICKSON | 247-4783
November 5, 2007
For more than a century, the comet known as 17P/Holmes has been too shy to shine. It would slip past Earth every seven years with a light so dim, the naked eye couldn't see it. Even astronomers largely ignored its fainter-than-faint, reliably uneventful visits.
But when an observer in the Canary Islands looked up into the northeast sky early on the morning of Oct. 24, an object where the dark comet should have been beamed so brightly that he couldn't explain it. Minutes later, the same strange object was spotted from Barcelona, Spain, by another equally bewildered stargazer.
In less than 24 hours, Comet 17P/Holmes had intensified so much that its once dark mass resembled a star, prompting a rash of excited sightings across the planet. Then — over the following few days — its brightness multiplied by a million times, making it not only visible to the unaided eye but also one of the most prominent objects in the night sky.
"This is the first naked-eye comet since Hale-Bopp in 1997 — so we're really pretty excited," said astronomy curator Kelly Ann Herbst of the Virginia Living Museum.
"Even without binoculars, you can see that this is a pretty big thing. It's immediately visible. And with a telescope, you can see not only the nucleus but also the details of the coma — this beautiful halo that ripples and changes over time."
Often referred to by astronomers as "17P" or "Comet Holmes," the celestial object's sudden outburst during the past couple of weeks echoes almost exactly its discovery on Nov. 6, 1892. Scanning the night sky, amateur English astronomer Edwin Holmes was so startled by its unexpected appearance that he scared his wife, who heard his exclamation from the next room.
After fading somewhat in the weeks that followed, the comet erupted again on Jan. 16. Not long afterward, it fell off the radar screen almost completely until flaring up again.
"Just like now, everybody was amazed — and they hoped to see it again," Herbst said. "But nobody could find it when they thought it should be coming around. This is only the second time the comet has had a period of outburst like this."
In terms of actual measured brightness, 17P has moved from a magnitude of 17, which is visible only through a large telescope, to somewhere just above magnitude 2. That's an increase of about 1 million times, Herbst said, and it makes the comet visible to the naked eye even in urban settings where the night sky is obscured by man-made light.
The comet also appears much bigger than it normally does, vaulting from imperceptible at first to the same size as Jupiter. In recent days, it's surpassed the giant planet, too, giving Herbst and many other night observers in the local area something totally unexpected to see.
Lawrence Taylor, a NASA Langley atmospheric scientist who's a member of the Virginia Peninsula Astronomy/Stargazers group, could barely wait for the trick-or-treaters to leave his Hampton home Halloween night so he could take a quick peek into the heavens.
So impressive was the sight that he ended up staying outside until 1 a.m. — all the while shuttling larger and better pieces of equipment out into his yard.
"I was just going to take a quick look with the binoculars, but then I saw this huge thing — a great big fuzzy ball," he said. "The fact that you could see it with the naked eye — even with a quarter moon — is pretty amazing. It's just awesome — and it could be up there a couple of weeks."
Just how long 17P's surprising outburst will last remains to be determined. But right now, its unexpected behavior can be seen not long after dusk — and at an unusually favorable time of the lunar cycle.
"The moon is waning now, so we'll have some really dark nights to see the sun reflecting off its dust," Herbst says. "It's really just perfect."
Both the Living Museum and the Peninsula Stargazers plan to stage numerous public observing sessions over the next few weeks, including such relatively dark and undisturbed viewing locations as York River State Park in James City County and Grundland Park in the Grandview section of Hampton.
But even in Newport News, where Herbst has been following Comet Holmes with the museum's big 16-inch-diameter telescope, the sight of the large golden ball rising in the northeast sky has been compelling.
"You can't see the tail because it's extended out behind it. But it's still really quite spectacular," Herbst said. "It has this huge envelope of dust and gas surrounding the nucleus — and it's so big that it almost fills the field of vision on our largest telescope."
Copyright © 2007, Newport News, Va., Daily Press
