Interessante objecten:quote:Sky Calendar
February 2007
All times ET unless noted
By Larry Sessions
February
Friday, 02/02
Full Moon, 12:45 a.m.
Signifying a time of harsh conditions, this Moon was called "The Moon of Frost in the Tipi" by the Lakota, and the "Hunger Moon" by the Osage.
Friday, 02/02
Moon-Saturn, 6:00 p.m.
The Moon passes less than a degree to the North of Saturn in Leo. This occurs before moonrise in most locations, although right at moonrise in some eastern locales of North America. From parts of Asia and the Arctic it can be viewed as an occultation.
Wednesday, 02/07
Mercury at Greatest Elongation East, noon
Like Venus, Mercury oscillates back in forth. sometimes to the left or evening sky side of the Sun, sometimes to the right or morning side. When it reaches its greatest distance one side or the other, it is called an "elongation." Today it is at its greatest elongation East for the current orbit. It is about 18 degrees to the East of the Sun, and can be found low in the West-southwest just after sunset.
Wednesday, 02/07
Moon passes Spica, 11:00 p.m.
The Moon passes near the star Spica in Virgo. Occurring before moonrise in North America for all but certain East Coast locations, the two are still fairly close but more widely separated for points West. Observers in parts of far southern South America see an occultation.
Saturday, 02/10
Last Quarter Moon, 4:51 a.m.
The "mirror image" (well, not really, but at first glance it looks that way) of the First Quarter Moon. It's really more like the opposite of First Quarter. Each phase illuminates opposite halves of the Moon's visible surface. Whereas First Quarter Moons rise at about noon and set at about midnight, Last Quarter Moons do the opposite -- they rise at about midnight and set at about noon.
Saturday, 02/17
New Moon, 2:14 p.m.
New Moon, per se, cannot be seen, but some observers go to great efforts to observe the thin Crescent Moons either a day or so before or a day or so after New Moon. In this case, you can't see the Moon tonight, but you can try looking to the West about a half hour to 45 minutes after sunset. If you don't catch it on Sunday evening, try again on Monday, when it should be easier -- and Venus is nearby..
Monday, 02/19
Moon-Venus, dusk
The Crescent Moon passes a few degrees above Venus tonight in the western dusk. (The closest approach between the two -- about two degrees -- comes at roughly noon.) Look within about an hour to 90 minutes after sunset. If you wait much later, they will have set.
Friday, 02/23
Moon-Pleiades, early evening (6 p.m.)
The First Quarter Moon (see tomorrow) passes about a degree to the North of the Pleiades star cluster (M45). High in the sky for most observers, this is a nice sight in binoculars.
Saturday, 02/24
First Quarter Moon, 2:56 a.m.
The Moon is one quarter of the way through its current cycle of phases, hence the name, "First Quarter." You can also think of it as being a quarter, but that is how much of the Moon's surface we see at this time. At any given time, only 50 percent of the Moon is potentially visible here on Earth, the other 50 percent being the side turned away from us. When just 50 percent of the side turned toward us is illuminated (as is true with the quarter phases), then we see 50 percent of 50 percent, or 25 percent. Hence again, a quarter.
Thursday, 03/01
Moon-Saturn, 9 p.m.
The nearly Full Moon passes about a degree to the North of Saturn. In parts of Europe this is visible as an occultation (eclipse) of the planet by the Moon. Unfortunately in North America the occultation is not visible, but the close approach should prove a nice sight.
Saturday, 03/03
Full Moon, 6:17 p.m.
The third Full Moon of the year was the "Moon when the eyes are sore from the bright snow" by the Dakota Sioux, and similar names of the Lakota Sioux and Ponca. The Cherokee knew it as the month of the "Windy Moon," and the Natchez called it the "Deer Moon." This month, we might call it the "Shadow Moon." (See the next entry.) [Moon names from The Moon Book by Kim Long, Johnson Books, Boulder, 1998]
Saturday, 03/03
Total Lunar Eclipse, 5:44 p.m. (beginning of totality)
This lunar eclipse is visible in part from all of North America except Alaska, and parts of the Yukon and British Columbia. It is not visible from Hawaii. Observers east of a line from approximately the New Mexico-Arizona border northward through western Montana and central Alberta can observe at least some part of totality (which ends at 8:11 p.m. EST); Observers to the west of that line can see only a partial eclipse as the Moon rises. The time of maximum eclipse is 6:21 p.m. EST. Totality is already in progress at moonrise for all of North America except for Prince Edward Island and extreme eastern Newfoundland and Labrador. The partial phase is over at 9:24 p.m. EST. (For more information, see this article: eclipse.)
[Note: data for this calendar has been derived from a number of sources including the Observer’s Handbook 2007 of the Royal Astronomical Society of Canada, Starry Night software, and others.]
Nederlandse versie:quote:Op vrijdag 16 maart 2007 08:41 schreef Frutsel het volgende:
Huge Frozen Lake on Southpole of Mars
Mars is unlikely to sport beachfront property any time soon, but the planet has enough water ice at its south pole to blanket the entire planet in more than 30 feet of water if everything thawed out.
With a radar technique, astronomers have penetrated for the first time about 2.5 miles (nearly four kilometers) beneath the south pole's frozen surface.
[afbeelding]
The south polar layered ice deposits of Mars, with purple thinnest and red thickest. The black circle was not surveyed.
The data showed that nearly pure water ice lies beneath.
Discovered in the early 1970s, layered deposits of ice and dust cap the north and south poles of Mars. Until now, the deposits have been difficult to study closely with existing telescopes and satellites.
The current advance comes from a probe of the deposits using an instrument aboard the Mars Express orbiter.
"This is the first time that a ground-penetrating system has ever been used on Mars," said the new radar study's lead author, Jeffrey Plaut of NASA's Jet Propulsion Laboratory. "All the other instruments used to study the surface of Mars in the past really have only been sensitive to what occurs at the very surface."
(NASA's Mars Odyssey spacecraft also carries instruments designed, among other things, to probe beneath icy polar surfaces.)
Deep probe
Plaut and his colleagues probed the deposits with radar echo sounding, typically used on Earth to study the interiors of glaciers.
The instrument, called the Mars Advanced Radar for Subsurface and Ionospheric Sounding, or MARSIS, beams radio waves which penetrate the planet's surface and bounce off features having different electrical properties.
The reflected beams revealed that 90 percent or more of the frozen polar material is pure water ice, sprinkled with dust particles.
The scientists calculated that the water would form a 36-foot-deep ocean of sorts if spread over the Martian globe.
"It's the best evidence that's been obtained to date for that thickness," said Ken Herkenhoff, a planetary geologist at the U.S. Geological Survey in Flagstaff, Ariz., who studies the Martian polar regions. He was not involved in the current study.
Scientists have long known that Mars' north polar cap is a massive storehouse of water ice, and the current research team says they will use their radar technique to refine past estimates of its thickness and make-up.
Missing water
"These polar ice deposits are by far the largest reservoir of water or water ice that we know of on Mars," Plaut said.
That's a lot of water, but not enough to account for the flowing streams thought to meander along Mars' surface in the past.
"There's evidence that about 10 times or maybe even 100 times that much water has flowed across the surface of Mars to carve the various channels, the outflow valleys and other features we see in the images and topography data," Plaut told SPACE.com.
So where's the rest of the water?
One idea is that a subterranean plumbing system once ferried loads of water beneath the Martian surface.
Plaut said his team also will search for underground pools with the radar technique.
29-03-2007quote:Op vrijdag 30 maart 2007 12:45 schreef Frutsel het volgende:
Many planets may have double suns
The dual suns that rise and set over Luke Skywalker's homeworld in the film Star Wars may be more than just fantasy, according to data from Nasa.
In a classic scene from the 1977 movie, the hero gazes into the distance as two yellow suns set on the horizon.
Nasa's Spitzer Space Telescope has found that planetary systems are as common around double stars as they are around single stars, like our own Sun.
Details of the research have been published in the Astrophysical Journal.
the study, a team of researchers used an infrared camera on the Spitzer telescope to search for so-called dusty discs around binary, or double, stars.
Dusty discs are made from the leftover debris of planet formation.
"We knew the stars would be there, the question was whether there was a planet to be the place where you could stand and see these sunsets," said Karl Stapelfeldt, a scientist at Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California.
"The inference is getting stronger now that there must be such planets based on what Spitzer has found."
The presence of planets in dusty discs is thought likely, but is by no means certain.
In our Solar System, asteroids collide with each other and produce showers of dust and that is, we assume, what we're seeing in these other discs - the dust produced by the collision of two bigger bodies," lead author David Trilling, from the University of Arizona, told BBC News.
"We can infer that there are bigger bodies like asteroids. The next logical leap is that if there are processes that formed these bigger bodies like asteroids, those same processes may also have formed planets." (BBC)
======================================================
Volledige artikel ---> http://news.bbc.co.uk/1/hi/sci/tech/6506081.stm
30-03-2007quote:Op vrijdag 30 maart 2007 18:52 schreef ExperimentalFrentalMental het volgende:
[..]
29-03-2007
Ook veel dubbelsterren kunnen planeten hebben
[afbeelding]
Op sommige planeten zijn dubbele zonsondergangen te zien.
Sterrenkundigen hebben met behulp van de infraroodsatelliet Spitzer vastgesteld dat in dubbelstersystemen net zo vaak stofschijven voorkomen als rond enkelvoudige sterren. Dat maakt het waarschijnlijk dat ook veel dubbelsterren planeten hebben en, omgekeerd, dat er veel planeten zijn waar twee (of zelfs meer) zonnen aan de hemel staan.
Lange tijd is gedacht dat planeetvorming alleen mogelijk zou zijn in dubbelstersystemen waarin de beide componenten minstens duizend astronomische eenheden (150 miljard kilometer) uit elkaar stonden. Maar het onderzoek met Spitzer laat juist zien dat in zeer nauwe dubbelstersystemen méér stofschijven gevonden worden dan in wijde. In die gevallen blijken de dicht om elkaar draaiende sterren zelfs door één stofschijf omringd te zijn.
Het minst ‘planeetvriendelijk’ zijn dubbelsterren waarbij de twee sterren drie tot vijftig astronomische eenheden van elkaar verwijderd zijn.
(allesoversterrenkunde)
Vertaling: http://www.astroversum.nl(...)euws.3103200701.htmlquote:Op zondag 1 april 2007 18:36 schreef Frutsel het volgende:
NEW COMET! - COMET LOVEJOY HEADS FOR EARTH IN APRIL
A new comet has recently been discovered, and like the brilliant Comet McNaught from earlier this year, this latest discovery belongs to an Australian: Comet Lovejoy (C/2007 E2).
On March 15th, Terry Lovejoy of Thornlands, Queensland, Australia, discovered a 9th-magnitude comet in the southern constellation Indus the Indian. In reporting the find to the Central Bureau for Astronomical Telegrams (CBAT), in Cambridge, Massachusetts, Lovejoy described the comet as having a coma that appeared distinctly green in color, with a slight extension to the southwest.
Remarkably, Lovejoy made the discovery not with a telescope but using an off-the-shelf digital camera! In fact, it appears to be the very first case of the discovery of a comet discovered in this manner.
Lovejoy was using a Canon 350D with a zoom lens set to 200-mm focal length at f/2.8. Lovejoy spotted the object near the frame edge in 16 exposures of 90 seconds each. The images were obtained during a comet-hunting survey that Lovejoy has been conducting for more than two years.
The first independent confirmation was obtained by John Drummond (Possum Observatory, Gisborne, New Zealand) on March 16. He used a 41-cm reflector and visually estimated the magnitude as 9.5—about 15 times dimmer than the faintest sky objects that can be seen without optical aid. Drummond estimated the coma diameter as 2.6 arc minutes (roughly equal to about 1/12 that of the apparent width of the Moon).
The green comet is too dim to see with the naked eye, but it’s a nice target for backyard telescopes. The first official orbit was calculated by Brian G. Marsden of the CBAT on March 19. He took 36 precise positions spanning a three day interval and determined the comet's perihelion date (when it will sweep closest to the Sun—a distance of 101.3 million mi/163 million km.) as March 27. The comet's distinctive greenish hue seems to suggest that it is rich in cyanogens and diatomic carbon.
Unlike Comet McNaught, which took a southerly route after passing the Sun, Comet Lovejoy will be progressing north during April and will soon become favorably placed for observation for observers in the Northern Hemisphere. Also unlike Comet McNaught, Comet Lovejoy will (unfortunately) not become a naked-eye object; it probably will get no brighter than magnitude +7.5. That's still about two and a half times fainter than the faintest naked-eye star. But it still should continue to be an interesting object to follow with binoculars and small telescopes as it moves north during April.
For most northern observers, it will not be until the second week of April that Comet Lovejoy will emerge from out of the dawn twilight and be positioned low in the southeast sky.
It will be located between the constellations of Capricornus the Sea Goat and Sagittarius the Archer [sky map]. During April 20-25, the comet will appear to cross the Milky Way while passing through the southern half of Aquila the Eagle. This is also about the time when it will be passing closest to Earth (41 million mi/66 million km, Apr. 24-26) and should appear at its brightest. Toward month's end, it will glide between Lyra the Lyre and Hercules, and appearing to pass almost directly overhead at around 3 a.m. local daylight time.
On Comets ml—an Internet forum dedicated to the discussion of comets, Terry Lovejoy posted his thoughts after he made his discovery: "After a very intense search effort in 2006 without success, I had wound back my efforts in 2007 (partly because of fatigue!). March 15 was only the second time this year I had done any searches in the morning sky. All told I estimate I have examined about 1000 image fields since late 2004, which would equate to about 1000 hours. 2007 has been a good year with two lifetime astronomy goals finally achieved. The first goal was to see a daylight comet (McNaught) and the second to discover a comet."
"Mission accomplished!" (space.com)
Mooie afbeelding! Ook leuk idee voor een poster zodat je een beter overzicht hebt.quote:Op maandag 2 april 2007 16:16 schreef buachaille het volgende:
Alle hemellichamen uit ons zonnestelsel: http://kokogiak.com/solarsystembodieslargerthan200miles.html
Al was ik jullie dan zou ik deze link eens aanklikken.
Via: http://noorderlicht.vpro.nl/noorderlog/bericht/33958878/
Da's niet eens zo gek snel, 1 rondje per 10 seconden. Heb een half jaar terug een presentatie moeten houden over verschillende modellen voor neutronensterren, was erg interessant om te doen Impulsmomentbehoud zorgt voor de snelle rotatie ( ruwweg is m*v*r behouden, en als m niet al te veel afneemt en r fiks afneemt, dan neemt v flink toe ), en fluxbehoud ( ruwweg het magneetveld maal het oppervlak ) voor het gigantische veld; het oppervlak is immers evenredig met r2, en als r een factor 10 afneemt en de massaverdeling niet al te veel verandert, dan neemt B dus met een factor 100 toe.quote:Op vrijdag 6 april 2007 01:27 schreef ExperimentalFrentalMental het volgende:
04-04-2007
....
Hij staat op 15.000 lichtjaar afstand in het sterrenbeeld Ara, dat alleen vanaf het zuidelijk halfrond zichtbaar is. Hij draait elke tien seconden één keer om zijn as, waarbij een bundel van straling over de aarde zwiept.
In september 2006 werd de magnetar plotseling honderd keer zo helder, produceerde hij extra bundels van energierijke deeltjes en straling, en nam de rotatieperiode af met ongeveer een duizendste seconde. Volgens de onderzoekers is dit alles te verklaren door aan te nemen dat er spanningen in de korst van de neutronenster zijn opgetreden als gevolg van het 'ogpewonden' raken van magnetische veldlijnen. Dat leidde uiteindelijk tot een sterbeving, waarbij zeer veel energie vrijkwam.
(allesoversterrenkunde)
Thanks for the info beste Haushoferquote:Op woensdag 11 april 2007 11:48 schreef Haushofer het volgende:
[..]
Da's niet eens zo gek snel, 1 rondje per 10 seconden. Heb een half jaar terug een presentatie moeten houden over verschillende modellen voor neutronensterren, was erg interessant om te doen Impulsmomentbehoud zorgt voor de snelle rotatie ( ruwweg is m*v*r behouden, en als m niet al te veel afneemt en r fiks afneemt, dan neemt v flink toe ), en fluxbehoud ( ruwweg het magneetveld maal het oppervlak ) voor het gigantische veld; het oppervlak is immers evenredig met r2, en als r een factor 10 afneemt en de massaverdeling niet al te veel verandert, dan neemt B dus met een factor 100 toe.
Zo krijg je dus een snel roterende magnetisch geladen bol, wat een gigantisch elektrisch veld genereert ( vergelijk een roterende schijf in een magnetisch veld ) In bepaalde gebieden bij de polen kunnen deeltjes buiten de gesloten magneetveldlijnen komen, en hierdoor krijg je een " beam" van geladen deeltjes.
Er worden deeltjes gemeten die gigantische energieen hebben, en dit soort mechanismes zouden daar verantwoordelijk voor kunnen zijn.
Dit is echt vetquote:Op woensdag 25 april 2007 08:06 schreef ExperimentalFrentalMental het volgende:
25-04-2007
Bewoonbare planeet ontdekt bij rode dwergster
[afbeelding]
Illustratie van de bewoonbare planeet in een baan rond de rode dwergster Gliese 581.
Bij de rode dwergster Gliese 581 in het sterrenbeeld Weegschaal is een planeet ontdekt waar leven op zou kunnen voorkomen. De ster staat op ruim twintig lichtjaar afstand en is niet met het blote oog te zien. De nieuw ontdekte planeet is minstens vijf keer zo zwaar en anderhalf keer zo groot als de aarde, en voltooit elke dertien dagen een rondje om zijn moederster, op een afstand van minder dan elf miljoen kilometer. De temperatuur op de planeet wordt geschat op 0 tot 40 graden Celsius, zodat er op het rotsachtige hemellichaam in principe water zou kunnen voorkomen.
Het is voor het eerst dat een aarde-achtige planeet gevonden is in de 'bewoonbare zone' van een ster. De ontdekking is gedaan door een team van Zwitserse, Franse en Portugese astronomen, met een gevoelige spectrograaf op de 3,6-meter telescoop van de Europese Zuidelijke Sterrenwacht in Chili. Twee jaar geleden vond hetzelfde team al een veel zwaardere planeet bij de ster, in een nog kleinere baan. Ook buiten de bewoonbare planeet cirkelt nog een zware planeet rond.
(allesoversterrenkunde)
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