From Space.com:
Yahoo! Buzz
Venus' Atmosphere Proves a Real Drag, Leading to a Discovery
By Mike Wall
SPACE.com Senior Writer
posted: 07 October 2010
07:47 pm ET
A spacecraft using a bold new method to study Venus — flying directly through the planet's atmosphere — has found that the atmosphere at Venus' poles is thinner than expected.
The European Space Agency's Venus Express probe made the discovery during a series of dives through the atmosphere of Venus over the past two years. Scientists measured the drag on the spacecraft during these atmospheric dips to determine Venusian air density.
"It's really a very accurate and precise method," Venus Express project scientist Hakan Svedhem said at a news briefing Wednesday (Oct. 6). Svedhem and his colleagues presented their findings at the American Astronomical Society's Division of Planetary Sciences meeting in Pasadena, Calif.
The observations will help prepare Venus Express for one final, deep dive that will alter its orbit and extend its operational life, the researchers said.
Thinner than they thought
Venus Express' atmospheric dives revealed that the planet's polar atmosphere is about 60 percent thinner than predicted, researchers said. The team is trying to figure out what accounts for this surprising result.
The spacecraft's twisting motion during its dives also registered a sharp density change from Venus' day side to its night side, scientists said.
The Venus Express team is gearing up for another dive next week, when the probe will make its deepest foray yet into Venus' atmosphere — down to about 102 miles (165 kilometers) above the planet's surface.
This is getting closer to the aerobraking altitude that would adjust the probe's orbit, which Svedhem estimated to be about 87 miles (140 km) above the surface. But the team isn't ready to make this move yet.
"The timetable is still open because a number of studies have yet to be completed," Svedhem said. "If our experiments show we can carry out these maneuvers safely, then we may be able to lower the orbit in early 2012."
Changing course
Venus Express arrived at Venus in April 2006 and has been studying the planet's atmosphere ever since. The probe currently has a highly elliptical polar orbit that loops from 155 to 41,000 miles (250 to 66,000 km) above the Venusian surface.
When Venus Express is far away from the planet, the sun's gravity pulls it slightly off course. As a result, the spacecraft's engines must be fired every 40-50 days to compensate. The fuel to do this will run out in 2015.
Mission planners want to give the probe a chance to keep operating beyond 2015. So they're considering shaking things up and bringing Venus Express much closer to the planet, reducing its orbital period from 24 hours to 12.
To do this, scientists would dip Venus Express deep into the planet's atmosphere. The resulting drag would slow the spacecraft down and change its orbit. This maneuver is delicate and potentially risky, according to researchers.
"It would be dangerous to send the spacecraft deep into the atmosphere before we understand the density," team member Pascal Rosenblatt of the Royal Observatory of Belgium said in a statement.
However, Venus Express has no instruments capable of measuring this density directly, researchers said. So mission planners have improvised. They sent the probe skimming down into the alien atmosphere on exploratory dives — at altitudes of about 110 miles (180 km) — in July-August 2008, October 2009, February 2010 and April 2010.
During these jaunts, radio tracking stations on Earth watched for the drag exerted on the spacecraft. In addition, operators turned one of Venus Express' solar wings edge-on and the other face-on so that air resistance twisted the spacecraft, researchers said.
Earth--Day and Night Regions
Thursday, October 7, 2010
Friday, October 1, 2010
Comet Hartley 2 To Have Close Encounter With Earth This Month
From Space.com:
Comet and Earth to Have Rare Close Encounter
By Joe Rao
SPACE.com Skywatching Columnist
posted: 01 October 2010
08:41 am ET
Typically during the course of a year about a dozen comets will come within the range of amateur telescopes. Most quietly come and go with little fanfare, but during the upcoming weeks one rather small comet will be making an unusually close approach to the Earth.
On Oct. 20, Comet Hartley 2 will pass just over 11 million miles (18 million km) from Earth. During October it should be easily visible in small telescopes, binoculars and — from sites with dark enough skies — even with the naked eye.
This video sky map shows how to spot the comet.
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wallpapers.smileycentral.comComets are composed of rock, dust, water ice and frozen gases such as carbon monoxide, carbon dioxide, methane and ammonia. [Best Comet Appearances of All Time]
Because of their low mass, comet nuclei do not become spherical under their own gravity as larger bodies in space do, and thus have irregular shapes. They are often popularly described as "dirty snowballs," though recent observations have revealed dry dusty or rocky surfaces, suggesting that the ices are hidden beneath the crust.
In addition to its close pass of Earth, Comet Hartley 2 will be visited in early November by the Deep Impact spacecraft, which already had a previous encounter with Comet Tempel 1 in 2005.
Hartley's discovery
Back on March 15, 1986, astronomer Malcolm Hartley discovered a new comet on photographic images taken at the U.K. Schmidt Telescope Unit at Siding Spring, Australia.
At the time Hartley discovered it, the newfound comet was an exceedingly faint object, with just a hint of a tail; it was about 25,000 times dimmer than the faintest stars that can be seen with the naked eye. After further images were obtained over the next several days, Hartley announced his discovery to the Central Bureau for Astronomical Telegrams in Cambridge, Mass.
This was Hartley's second discovery of a comet and so was designated as Comet Hartley 2. Orbital calculations by Brian Marsden of the Smithsonian Astrophysical Observatory in Cambridge, Mass., indicated that Hartley 2 had already made its closest approach to the sun nine months earlier and that at that time it was too close to the sun's glare to have been detected.
Marsden also calculated that the comet made a close approach to Jupiter during 1982. The comet takes roughly 6 1/2 years to circle the sun and it has since been observed again in 1991, 1997 and 2004.
Rare close encounter
This fall, Comet Hartley 2 will again be passing through the inner solar system, reaching its closest point to the sun (called perihelion) on Oct. 28 at a distance of 98.4 million miles (158.4 million km).
And while en route to the sun, it will also make a very close approach to the Earth. In fact, at 3 p.m. ET on Oct. 20, the comet will be at its closest point to our planet at a distance of 11.2 million miles (18 million km).
It's quite unusual for any comet to approach this close to Earth. Such an event only happens on average perhaps three or four times a century.
If this comet were reasonably large, it would likely put on a very spectacular show around the time of its closest approach.
Halley's Comet passed a similar distance from Earth in the year 1066 and was described in ancient records as appearing "like a moon" as well as being depicted in the Bayeux Tapestry, a long embroidered piece of cloth that depicts the Norman conquest of England.
A small, faint comet
Unfortunately, Hartley 2 is a very small and intrinsically faint comet. Observations by the Spitzer Space Telescope in August 2008 showed that the comet's nucleus has a diameter of just 0.7 miles (1.1 km). Its nucleus is only about one tenth the size of Halley's Comet and perhaps only one thirtieth that of Comet Hale-Bopp.
Nonetheless, Hartley 2 will come close enough to us to become dimly visible to the unaided eye during early to mid October.
Astronomers use magnitude to define the brightness of sky objects; the lower the magnitude, the brighter the object. The brightest stars are zero or first magnitude, while the faintest stars are sixth magnitude.
Current expectation is that the comet will reach a peak magnitude of perhaps 4.4 at the time of its closest approach. However, around that time the comet will probably appear very large in overall apparent size, perhaps similar to the apparent size of the full moon.
As a result, much of the comet's brightness will be "spread out" over that area of the sky. So visually to the eye under a dark sky it will appear not as a sharp star-like image, but more like a dim, circular patch of light.
Binoculars or a small low-power telescope will provide a somewhat more pleasing view: a dim, circular, grayish-blue ball of light with a star-like condensation (the nucleus) at the center.
If the comet develops a tail of any kind, it likely will be of the gaseous variety — very thin, faint and narrow, giving the comet the appearance of what comet expert John Bortle likens to "an apple on a stick."
Where to find it
As October begins, Comet Hartley 2 will be in the constellation of Cassiopeia, which at dusk will be positioned halfway up in the northeast sky; through Oct. 5 it will be passing below and to the right of the famous "W"-shaped formation composed of five bright stars.
The comet then moves into the constellation of Perseus on Oct. 6 and before dawn on the morning of Oct. 8, it will be situated only 0.7 degrees below and to the right of the famous Double Star Cluster. The cluster supposedly marks the sword handle of Perseus and is often touted as one of the most impressive star clusters in the entire sky.
On the morning of Oct. 10, the comet will appear to almost touch the 4th-magnitude star, Eta Persei. On Oct. 17, it will enter the boundaries of the constellation Auriga, and on the morning of Oct. 18, Hartley 2 will be about 1.2 degrees above and to the right of the star Epsilon Aurigae and 3 degrees below and to the right of the brilliant zero-magnitude star Capella.
Between Oct. 15 and 20, within about a half hour of 4:00 a.m. local time, the comet will be passing almost directly overhead.
Moon muscles In
But one problem that will become an increasing factor during the middle of October is the waxing moon that will light up the sky during the first part of the night and will seriously interfere with observations of the comet.
The moon will set later in the night leaving the sky dark during the predawn hours, but as it approaches its full phase on Oct. 22, the amount of time between moonset and the first light of dawn will get noticeably shorter.
For example: From mid-northern latitudes on Oct. 16, moonset is at 12:56 a.m. local time and dawn breaks at 5:37 a.m., which means the sky will be dark and moonless for 4 hours and 41 minutes.
Just four mornings later, however, the nearly full moon will set at 4:51 a.m. with morning twilight beginning at 5:41 a.m., leaving just a scant 50 minutes of dark sky for comet viewing. On Oct. 21, the moon will not set until 5:51 a.m. or 9 minutes after dawn.
Coming Attractions
Even after Hartley 2 makes its closest approach to Earth, it will become part of another close approach of a different kind. On Sept. 5, more than five years after its July 4, 2005, rendezvous with Comet Tempel 1, NASA's Deep Impact spacecraft will begin beaming down the first of more than 64,000 images it's expected to take of Comet Hartley 2.
The spacecraft will continue imaging Hartley 2 during and after its closest approach on Nov. 4, when it will pass to within 430 miles (692 km) of the comet's nucleus, providing an extended look at the comet.
The flyby of Comet Hartley 2 is the second leg of the Deep Impact spacecraft's two-part extended mission known as EPOXI. During the flyby a science team from the University of Maryland will study the comet using all three of the spacecraft's instruments — two telescopes with digital color cameras and an infrared spectrometer.
Gallery: The Great Comet McNaught: Part 1, Part 2
The Best Comets of All Time
Astrophotography Telescopes for Beginners
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
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posted 01 October 2010, 11:00 am ETgordon_flash wrote:
Unfortunately the map doesn't help much. There's no cross, or dot, or anything to show the position of the comet relative to the label or to the dashed curve which, I assume, is the track of the comet in the sky (moving from right to left, according to the article).
Still, I'll doggedly have a look and see if I can spot it. Maybe it will surprise us!
.Reply
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Report Abuse
Expand to View Replies (1). posted 01 October 2010, 1:16 pm ETernestborg9 wrote:
This does suck balls to be certain...such a huge failure on the part of the author. Try this link...to sky and telescope's sky map:
http://media.skyandtelescope.com/images/CometHartley2-bw.jpg
.Recommend (0)
Report Abuse.
Comet and Earth to Have Rare Close Encounter
By Joe Rao
SPACE.com Skywatching Columnist
posted: 01 October 2010
08:41 am ET
Typically during the course of a year about a dozen comets will come within the range of amateur telescopes. Most quietly come and go with little fanfare, but during the upcoming weeks one rather small comet will be making an unusually close approach to the Earth.
On Oct. 20, Comet Hartley 2 will pass just over 11 million miles (18 million km) from Earth. During October it should be easily visible in small telescopes, binoculars and — from sites with dark enough skies — even with the naked eye.
This video sky map shows how to spot the comet.
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Maps.alot.comYour Name Is No Accident27 Facts You Don't Know About Your Personality and Future. But Should!
Numerologist.comFree Space WallpapersGet Cool Space Desktop Wallpapers w Planets, Moons & Stars-Try Them Now
wallpapers.smileycentral.comComets are composed of rock, dust, water ice and frozen gases such as carbon monoxide, carbon dioxide, methane and ammonia. [Best Comet Appearances of All Time]
Because of their low mass, comet nuclei do not become spherical under their own gravity as larger bodies in space do, and thus have irregular shapes. They are often popularly described as "dirty snowballs," though recent observations have revealed dry dusty or rocky surfaces, suggesting that the ices are hidden beneath the crust.
In addition to its close pass of Earth, Comet Hartley 2 will be visited in early November by the Deep Impact spacecraft, which already had a previous encounter with Comet Tempel 1 in 2005.
Hartley's discovery
Back on March 15, 1986, astronomer Malcolm Hartley discovered a new comet on photographic images taken at the U.K. Schmidt Telescope Unit at Siding Spring, Australia.
At the time Hartley discovered it, the newfound comet was an exceedingly faint object, with just a hint of a tail; it was about 25,000 times dimmer than the faintest stars that can be seen with the naked eye. After further images were obtained over the next several days, Hartley announced his discovery to the Central Bureau for Astronomical Telegrams in Cambridge, Mass.
This was Hartley's second discovery of a comet and so was designated as Comet Hartley 2. Orbital calculations by Brian Marsden of the Smithsonian Astrophysical Observatory in Cambridge, Mass., indicated that Hartley 2 had already made its closest approach to the sun nine months earlier and that at that time it was too close to the sun's glare to have been detected.
Marsden also calculated that the comet made a close approach to Jupiter during 1982. The comet takes roughly 6 1/2 years to circle the sun and it has since been observed again in 1991, 1997 and 2004.
Rare close encounter
This fall, Comet Hartley 2 will again be passing through the inner solar system, reaching its closest point to the sun (called perihelion) on Oct. 28 at a distance of 98.4 million miles (158.4 million km).
And while en route to the sun, it will also make a very close approach to the Earth. In fact, at 3 p.m. ET on Oct. 20, the comet will be at its closest point to our planet at a distance of 11.2 million miles (18 million km).
It's quite unusual for any comet to approach this close to Earth. Such an event only happens on average perhaps three or four times a century.
If this comet were reasonably large, it would likely put on a very spectacular show around the time of its closest approach.
Halley's Comet passed a similar distance from Earth in the year 1066 and was described in ancient records as appearing "like a moon" as well as being depicted in the Bayeux Tapestry, a long embroidered piece of cloth that depicts the Norman conquest of England.
A small, faint comet
Unfortunately, Hartley 2 is a very small and intrinsically faint comet. Observations by the Spitzer Space Telescope in August 2008 showed that the comet's nucleus has a diameter of just 0.7 miles (1.1 km). Its nucleus is only about one tenth the size of Halley's Comet and perhaps only one thirtieth that of Comet Hale-Bopp.
Nonetheless, Hartley 2 will come close enough to us to become dimly visible to the unaided eye during early to mid October.
Astronomers use magnitude to define the brightness of sky objects; the lower the magnitude, the brighter the object. The brightest stars are zero or first magnitude, while the faintest stars are sixth magnitude.
Current expectation is that the comet will reach a peak magnitude of perhaps 4.4 at the time of its closest approach. However, around that time the comet will probably appear very large in overall apparent size, perhaps similar to the apparent size of the full moon.
As a result, much of the comet's brightness will be "spread out" over that area of the sky. So visually to the eye under a dark sky it will appear not as a sharp star-like image, but more like a dim, circular patch of light.
Binoculars or a small low-power telescope will provide a somewhat more pleasing view: a dim, circular, grayish-blue ball of light with a star-like condensation (the nucleus) at the center.
If the comet develops a tail of any kind, it likely will be of the gaseous variety — very thin, faint and narrow, giving the comet the appearance of what comet expert John Bortle likens to "an apple on a stick."
Where to find it
As October begins, Comet Hartley 2 will be in the constellation of Cassiopeia, which at dusk will be positioned halfway up in the northeast sky; through Oct. 5 it will be passing below and to the right of the famous "W"-shaped formation composed of five bright stars.
The comet then moves into the constellation of Perseus on Oct. 6 and before dawn on the morning of Oct. 8, it will be situated only 0.7 degrees below and to the right of the famous Double Star Cluster. The cluster supposedly marks the sword handle of Perseus and is often touted as one of the most impressive star clusters in the entire sky.
On the morning of Oct. 10, the comet will appear to almost touch the 4th-magnitude star, Eta Persei. On Oct. 17, it will enter the boundaries of the constellation Auriga, and on the morning of Oct. 18, Hartley 2 will be about 1.2 degrees above and to the right of the star Epsilon Aurigae and 3 degrees below and to the right of the brilliant zero-magnitude star Capella.
Between Oct. 15 and 20, within about a half hour of 4:00 a.m. local time, the comet will be passing almost directly overhead.
Moon muscles In
But one problem that will become an increasing factor during the middle of October is the waxing moon that will light up the sky during the first part of the night and will seriously interfere with observations of the comet.
The moon will set later in the night leaving the sky dark during the predawn hours, but as it approaches its full phase on Oct. 22, the amount of time between moonset and the first light of dawn will get noticeably shorter.
For example: From mid-northern latitudes on Oct. 16, moonset is at 12:56 a.m. local time and dawn breaks at 5:37 a.m., which means the sky will be dark and moonless for 4 hours and 41 minutes.
Just four mornings later, however, the nearly full moon will set at 4:51 a.m. with morning twilight beginning at 5:41 a.m., leaving just a scant 50 minutes of dark sky for comet viewing. On Oct. 21, the moon will not set until 5:51 a.m. or 9 minutes after dawn.
Coming Attractions
Even after Hartley 2 makes its closest approach to Earth, it will become part of another close approach of a different kind. On Sept. 5, more than five years after its July 4, 2005, rendezvous with Comet Tempel 1, NASA's Deep Impact spacecraft will begin beaming down the first of more than 64,000 images it's expected to take of Comet Hartley 2.
The spacecraft will continue imaging Hartley 2 during and after its closest approach on Nov. 4, when it will pass to within 430 miles (692 km) of the comet's nucleus, providing an extended look at the comet.
The flyby of Comet Hartley 2 is the second leg of the Deep Impact spacecraft's two-part extended mission known as EPOXI. During the flyby a science team from the University of Maryland will study the comet using all three of the spacecraft's instruments — two telescopes with digital color cameras and an infrared spectrometer.
Gallery: The Great Comet McNaught: Part 1, Part 2
The Best Comets of All Time
Astrophotography Telescopes for Beginners
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
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www.Y-Jesus.com/JesusGodScience News and VideosWatch Science, Tech, Health Videos Learn something new today!
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Telescope-Pictures.best-price.comComments (2)
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posted 01 October 2010, 11:00 am ETgordon_flash wrote:
Unfortunately the map doesn't help much. There's no cross, or dot, or anything to show the position of the comet relative to the label or to the dashed curve which, I assume, is the track of the comet in the sky (moving from right to left, according to the article).
Still, I'll doggedly have a look and see if I can spot it. Maybe it will surprise us!
.Reply
Recommend (0)
Report Abuse
Expand to View Replies (1). posted 01 October 2010, 1:16 pm ETernestborg9 wrote:
This does suck balls to be certain...such a huge failure on the part of the author. Try this link...to sky and telescope's sky map:
http://media.skyandtelescope.com/images/CometHartley2-bw.jpg
.Recommend (0)
Report Abuse.
Wednesday, September 29, 2010
U.S. Scientists Find Potentially Habitable Planet Near Earth
from Yahoo News and The Audacity of Hypocrisy:
US scientists find potentially habitable planet near Earthfrom Audacity Of Hypocrisy by adminUS astronomers said Wednesday they have discovered an Earth-sized planet that they think might be habitable, orbiting a nearby star, and believe there could be many more planets like it in space.
The planet, found by astronomers at the University of California, Santa Cruz, and the Carnegie Institution of Washington, is orbiting in the middle of the “habitable zone” of the red dwarf star Gliese 581, which means it could have water on its surface.
Liquid water and an atmosphere are necessary for a planet to possibly sustain life, even it it might not be a great place to live, the scientists said.
The scientists determined that the planet, which they have called Gliese 581g, has a mass three to four times that of Earth and an orbital period of just under 37 days.
Its mass indicates that it is probably a rocky planet and has enough gravity to hold on to an atmosphere, according to Steven Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz, and one of the leaders of the team that discovered the planet.
(Excerpt) Read more at news.yahoo.com
And, from Space.com:
Alien World Tour: The Exoplanets Around Star Gliese 581
By Mike Wall
SPACE.com Senior Writer
posted: 29 September 2010
06:55 pm ET
The announcement today of two newfound alien planets circling the star Gliese 581 adds to the nearby solar system's intrigue, further cementing its status as a top candidate to harbor extraterrestrial life.
One of the two newly discovered planets, known as Gliese 581g, is a small, Earth-like world that likely lies within its star's habitable zone — the just-right range of distances that allow liquid water to exist. [Artist's conception of Gliese 581g.]
Astronomers have now detected six planets orbiting Gliese 581, the most known to circle any star beyond our own sun. Here's a brief tour of the star and its planets, from the inside out:
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Maps.alot.comGliese 581: the mother star
Gliese 581 is a red dwarf located 20.5 light-years from Earth, in the constellation Libra. Like other red dwarfs, it's smaller and much dimmer than our sun. Scientists believe Gliese 581 is old — at least a few billion years — and relatively stable. Both are qualities conducive to the evolution of life, scientists have said.
Nearest planet
The nearest planet to the star is Gliese 581e, a rocky world nearly twice as massive as Earth.
Gliese 581e is extremely close to its parent star — it completes an orbit every 3.15 days — so it's likely far too hot for life to have any chance of taking root.
Gliese 581e is about 0.033 astronomical units from its parent star. One astronomical unit, or AU, is the average distance between the Earth and sun, about 93 million miles (150 million km).
Astronomers announced this planet's discovery in April 2009, and it's in the running for the lightest known extrasolar planet. So far, the only potential alien planet less massive than Gliese 581e is a world about 1.4 times the mass of Earth, but its existence — around a more distant star — has not yet been confirmed.
Next up: Gliese 581b
Traveling outward, the next planet is Gliese 581b, a Neptune-size alien world that's about 16 times as massive as Earth. This planet is still very close to the star, completing an orbit in 5.4 days.
Astronomers first discovered this planet in December 2005, according to an extrasolar planet database maintained by NASA's Jet Propulsion Laboratory. Its average distance from the Gliese 581 star is about 0.041 AU.
Rocky world in third
Gliese 581c comes next. This is a rocky, smallish planet — about five Earth masses — that makes a full trip around the red dwarf every 15 days.
Astronomers once thought Gliese 581c might be in the habitable zone, but later observations suggested the planet is likely too hot to support liquid water or life. The planet is about 0.073 AU from its parent star.
Meet Gliese 581g
Unlike Gliese 581c, the newfound planet Gliese 581g looks much more hospitable. It is orbiting within the habitable zone of its parent star.
Gliese 581g is three to four times as massive as Earth, is most likely rocky, and may have an atmosphere, scientists say. It orbits about 0.146 AU from the central star.
Liquid water could exist on some part of the planet's surface, which seems to have an average temperature between minus 24 and minus 10 degrees Fahrenheit (minus 31 to minus 12 degrees Celsius). Gliese 581g completes an orbit every 37 days or so.
Fifth planet is a super-Earth
The next planet in line is a so-called super-Earth, Gliese 581d, which is seven or eight times as massive as Earth and completes an orbit every 67 days.
Though at first glance this planet appeared to be beyond the star's habitable zone, astronomers think it might just squeak in — computer models suggest a greenhouse effect could be warming its surface. It was discovered in April 2007 and orbits about 0.22 AU from its parent star.
Sixth planet on the outskirts
The outermost planet in the Gliese 581 system (that astronomers know about, anyway) is the newly discovered Gliese 581f, announced today.
This planet is much farther away than the other five planets, zipping through space far outside the habitable zone, but it is still closer to its parent star than the Earth is to our sun. The planet is about 0.76 AU from its parent star.
Like all of the planets in the Gliese 581 system — and in our own solar system — Gliese 581f's orbit is nearly circular, scientists said.
US scientists find potentially habitable planet near Earthfrom Audacity Of Hypocrisy by adminUS astronomers said Wednesday they have discovered an Earth-sized planet that they think might be habitable, orbiting a nearby star, and believe there could be many more planets like it in space.
The planet, found by astronomers at the University of California, Santa Cruz, and the Carnegie Institution of Washington, is orbiting in the middle of the “habitable zone” of the red dwarf star Gliese 581, which means it could have water on its surface.
Liquid water and an atmosphere are necessary for a planet to possibly sustain life, even it it might not be a great place to live, the scientists said.
The scientists determined that the planet, which they have called Gliese 581g, has a mass three to four times that of Earth and an orbital period of just under 37 days.
Its mass indicates that it is probably a rocky planet and has enough gravity to hold on to an atmosphere, according to Steven Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz, and one of the leaders of the team that discovered the planet.
(Excerpt) Read more at news.yahoo.com
And, from Space.com:
Alien World Tour: The Exoplanets Around Star Gliese 581
By Mike Wall
SPACE.com Senior Writer
posted: 29 September 2010
06:55 pm ET
The announcement today of two newfound alien planets circling the star Gliese 581 adds to the nearby solar system's intrigue, further cementing its status as a top candidate to harbor extraterrestrial life.
One of the two newly discovered planets, known as Gliese 581g, is a small, Earth-like world that likely lies within its star's habitable zone — the just-right range of distances that allow liquid water to exist. [Artist's conception of Gliese 581g.]
Astronomers have now detected six planets orbiting Gliese 581, the most known to circle any star beyond our own sun. Here's a brief tour of the star and its planets, from the inside out:
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Maps.alot.comGliese 581: the mother star
Gliese 581 is a red dwarf located 20.5 light-years from Earth, in the constellation Libra. Like other red dwarfs, it's smaller and much dimmer than our sun. Scientists believe Gliese 581 is old — at least a few billion years — and relatively stable. Both are qualities conducive to the evolution of life, scientists have said.
Nearest planet
The nearest planet to the star is Gliese 581e, a rocky world nearly twice as massive as Earth.
Gliese 581e is extremely close to its parent star — it completes an orbit every 3.15 days — so it's likely far too hot for life to have any chance of taking root.
Gliese 581e is about 0.033 astronomical units from its parent star. One astronomical unit, or AU, is the average distance between the Earth and sun, about 93 million miles (150 million km).
Astronomers announced this planet's discovery in April 2009, and it's in the running for the lightest known extrasolar planet. So far, the only potential alien planet less massive than Gliese 581e is a world about 1.4 times the mass of Earth, but its existence — around a more distant star — has not yet been confirmed.
Next up: Gliese 581b
Traveling outward, the next planet is Gliese 581b, a Neptune-size alien world that's about 16 times as massive as Earth. This planet is still very close to the star, completing an orbit in 5.4 days.
Astronomers first discovered this planet in December 2005, according to an extrasolar planet database maintained by NASA's Jet Propulsion Laboratory. Its average distance from the Gliese 581 star is about 0.041 AU.
Rocky world in third
Gliese 581c comes next. This is a rocky, smallish planet — about five Earth masses — that makes a full trip around the red dwarf every 15 days.
Astronomers once thought Gliese 581c might be in the habitable zone, but later observations suggested the planet is likely too hot to support liquid water or life. The planet is about 0.073 AU from its parent star.
Meet Gliese 581g
Unlike Gliese 581c, the newfound planet Gliese 581g looks much more hospitable. It is orbiting within the habitable zone of its parent star.
Gliese 581g is three to four times as massive as Earth, is most likely rocky, and may have an atmosphere, scientists say. It orbits about 0.146 AU from the central star.
Liquid water could exist on some part of the planet's surface, which seems to have an average temperature between minus 24 and minus 10 degrees Fahrenheit (minus 31 to minus 12 degrees Celsius). Gliese 581g completes an orbit every 37 days or so.
Fifth planet is a super-Earth
The next planet in line is a so-called super-Earth, Gliese 581d, which is seven or eight times as massive as Earth and completes an orbit every 67 days.
Though at first glance this planet appeared to be beyond the star's habitable zone, astronomers think it might just squeak in — computer models suggest a greenhouse effect could be warming its surface. It was discovered in April 2007 and orbits about 0.22 AU from its parent star.
Sixth planet on the outskirts
The outermost planet in the Gliese 581 system (that astronomers know about, anyway) is the newly discovered Gliese 581f, announced today.
This planet is much farther away than the other five planets, zipping through space far outside the habitable zone, but it is still closer to its parent star than the Earth is to our sun. The planet is about 0.76 AU from its parent star.
Like all of the planets in the Gliese 581 system — and in our own solar system — Gliese 581f's orbit is nearly circular, scientists said.
Thursday, September 23, 2010
Spectacular Aurora On Saturn Shines In New Video
From Space.com:
Yahoo! Buzz
Spectacular Aurora on Saturn Shines in New Video
By SPACE.com Staff
posted: 23 September 2010
06:21 pm ET
Earth isn't the only planet in the solar system with a dazzling northern lights show. A new video from Saturn shows spectacular aurora on the ringed planet, revealing new details about how the phenomenon works.
The Saturn aurora movie was made from images collected by NASA's Cassini spacecraft's visual and infrared mapping spectrometer (VIMS) instrument. [Video of Saturn auroras.]
http://www.space.com/common/media/video/player.php?videoRef=SP_100923_saturn-aurora
"Cassini's instruments have been imaging the aurora in magnificent detail, but to understand the overall nature of the auroral region we need to make a huge number of observations -- which can be difficult because Cassini observation time is in high demand," said study leader Tom Stallard of the U.K.'s University of Leicester in a statement. "However, there are VIMS observations of numerous other scientific targets that also include auroral information. Sometimes the aurora can be clearly seen, sometimes we have to add multiple images together to produce a signal."
As a whole, the collection of observations should help build up a better understanding of how auroras happen across the solar system, he said.
Stallard will present preliminary results from his study at the European Planetary Science Congress in Rome on Friday (Sept. 24).
In the new Cassini video, the aurora can clearly be seen to vary significantly over the course of a Saturnian day, which lasts around 10 hours and 47 minutes. On the noon and midnight sides (to the left and right respectively) the aurora can be seen to brighten significantly for periods of several hours, suggesting the brightening is connected with the direction of the sun.
Other features can be seen rotating along with the underlying planet, reappearing at the same time and the same place on the second day. This suggests that they are directly controlled by the direction of Saturn's magnetic field, researchers said.
As with Earth's northern and southern lights, the auroras on Saturn are created when solar wind particles are channeled into the planet's magnetic field toward its poles. There, they interact with electrically charged gas (plasma) in the upper atmosphere and emit light.
However, aurora features on Saturn can also be caused by electromagnetic waves generated when its moons move through the plasma that fills the planet's magnetosphere.
To date, Stallard and his colleagues have investigated some 1,000 images from the 7,000 that Cassini's VIMS instrument has recorded of Saturn's auroral region.
"Saturn's aurorae are very complex and we are only just beginning to understand all the factors involved," Stallard said. "This study will provide a broader view of the wide variety of different auroral features that can be seen, and will allow us to better understand what controls these changes in appearance."
Yahoo! Buzz
Spectacular Aurora on Saturn Shines in New Video
By SPACE.com Staff
posted: 23 September 2010
06:21 pm ET
Earth isn't the only planet in the solar system with a dazzling northern lights show. A new video from Saturn shows spectacular aurora on the ringed planet, revealing new details about how the phenomenon works.
The Saturn aurora movie was made from images collected by NASA's Cassini spacecraft's visual and infrared mapping spectrometer (VIMS) instrument. [Video of Saturn auroras.]
http://www.space.com/common/media/video/player.php?videoRef=SP_100923_saturn-aurora
"Cassini's instruments have been imaging the aurora in magnificent detail, but to understand the overall nature of the auroral region we need to make a huge number of observations -- which can be difficult because Cassini observation time is in high demand," said study leader Tom Stallard of the U.K.'s University of Leicester in a statement. "However, there are VIMS observations of numerous other scientific targets that also include auroral information. Sometimes the aurora can be clearly seen, sometimes we have to add multiple images together to produce a signal."
As a whole, the collection of observations should help build up a better understanding of how auroras happen across the solar system, he said.
Stallard will present preliminary results from his study at the European Planetary Science Congress in Rome on Friday (Sept. 24).
In the new Cassini video, the aurora can clearly be seen to vary significantly over the course of a Saturnian day, which lasts around 10 hours and 47 minutes. On the noon and midnight sides (to the left and right respectively) the aurora can be seen to brighten significantly for periods of several hours, suggesting the brightening is connected with the direction of the sun.
Other features can be seen rotating along with the underlying planet, reappearing at the same time and the same place on the second day. This suggests that they are directly controlled by the direction of Saturn's magnetic field, researchers said.
As with Earth's northern and southern lights, the auroras on Saturn are created when solar wind particles are channeled into the planet's magnetic field toward its poles. There, they interact with electrically charged gas (plasma) in the upper atmosphere and emit light.
However, aurora features on Saturn can also be caused by electromagnetic waves generated when its moons move through the plasma that fills the planet's magnetosphere.
To date, Stallard and his colleagues have investigated some 1,000 images from the 7,000 that Cassini's VIMS instrument has recorded of Saturn's auroral region.
"Saturn's aurorae are very complex and we are only just beginning to understand all the factors involved," Stallard said. "This study will provide a broader view of the wide variety of different auroral features that can be seen, and will allow us to better understand what controls these changes in appearance."
Wednesday, September 22, 2010
Mercury's Comet-Like Tail Spotted By Amateur Astronomer
From Space.com:
Mercury's Comet-Like Tail Spotted by Amateur Astronomer
By SPACE.com Staff
posted: 22 September 2010
04:08 pm ET
Two satellites peering at the sun have snapped photos of Mercury's long, comet-like tail, but it took an amateur astronomer to bring the pictures to light.
The twin satellites are part of NASA's Stereo (Solar Terrestrial Relations Observatory) mission. They zip around the sun in Earth's orbit, one behind our planet and one ahead of it. Their main job is to monitor the sun and its atmosphere.
Since Mercury is so close to the sun, the planet occasionally wanders into the satellites' photos. Some of these images show a long, comet-like tail streaming off the planet, away from the sun. [New photo of Mercury tail.]
Astronomers didn't notice the tail in the photos right away. But it didn't escape the eyes of Australian medical researcher Ian Musgrave.
Musgrave was poring over an Internet database of images when he discovered Mercury's wispy tail. He then asked scientists at Boston University to take a look, university researchers said.
The scientists presented their findings at the European Planetary Science Congress meeting in Rome today (Sept. 22).
Mercury's tail
Scientists have known for years that Mercury has a long tail. From Earth it can be seen by analyzing light from sodium gas sputtered off Mercury's surface. The sun's intense radiation pressure pushes many sodium atoms off into space, creating a tail that extends far beyond the planet.
Mercury also has several smaller tails made of other gases. NASA's Messenger satellite recently detected these as it flew by Mercury in preparation to orbit the planet, researchers said.
But there are many details still to be worked out about these mysterious tails, and the new solar-satellite data should shed some light, researchers said.
"What makes the Stereo detections so interesting is that the brightness levels seem to be too strong to be from sodium," said study researcher Carl Schmidt of Boston University.
What's it made of?
The current focus of the team is to sort out what the gases in the tail might be.
The researchers are working to refine their brightness-calibration methods, and they're trying to determine the precise wavelengths of light that would get through the Stereo cameras' filters.
"The combination of our ground-based data with the new Stereo data is an exciting way to learn as much as possible about the sources and fates of gases escaping from Mercury," said researcher Michael Mendillo, also of Boston University.
Top 10 New Mysteries of Mercury
Mercury's Comet-Like Tail Spotted by Amateur Astronomer
By SPACE.com Staff
posted: 22 September 2010
04:08 pm ET
Two satellites peering at the sun have snapped photos of Mercury's long, comet-like tail, but it took an amateur astronomer to bring the pictures to light.
The twin satellites are part of NASA's Stereo (Solar Terrestrial Relations Observatory) mission. They zip around the sun in Earth's orbit, one behind our planet and one ahead of it. Their main job is to monitor the sun and its atmosphere.
Since Mercury is so close to the sun, the planet occasionally wanders into the satellites' photos. Some of these images show a long, comet-like tail streaming off the planet, away from the sun. [New photo of Mercury tail.]
Astronomers didn't notice the tail in the photos right away. But it didn't escape the eyes of Australian medical researcher Ian Musgrave.
Musgrave was poring over an Internet database of images when he discovered Mercury's wispy tail. He then asked scientists at Boston University to take a look, university researchers said.
The scientists presented their findings at the European Planetary Science Congress meeting in Rome today (Sept. 22).
Mercury's tail
Scientists have known for years that Mercury has a long tail. From Earth it can be seen by analyzing light from sodium gas sputtered off Mercury's surface. The sun's intense radiation pressure pushes many sodium atoms off into space, creating a tail that extends far beyond the planet.
Mercury also has several smaller tails made of other gases. NASA's Messenger satellite recently detected these as it flew by Mercury in preparation to orbit the planet, researchers said.
But there are many details still to be worked out about these mysterious tails, and the new solar-satellite data should shed some light, researchers said.
"What makes the Stereo detections so interesting is that the brightness levels seem to be too strong to be from sodium," said study researcher Carl Schmidt of Boston University.
What's it made of?
The current focus of the team is to sort out what the gases in the tail might be.
The researchers are working to refine their brightness-calibration methods, and they're trying to determine the precise wavelengths of light that would get through the Stereo cameras' filters.
"The combination of our ground-based data with the new Stereo data is an exciting way to learn as much as possible about the sources and fates of gases escaping from Mercury," said researcher Michael Mendillo, also of Boston University.
Top 10 New Mysteries of Mercury
Northern Lights Get Internet Reality Show
From Yahoo and Space.com:
Northern Lights Get Internet Reality Show
Buzz up!13 votes Share
retweet
EmailPrint..Tariq Malik
SPACE.com Managing Editor
SPACE.com tariq Malik
space.com Managing Editor
space.com – Mon Sep 20, 1:00 pm ET
This story was updated at 12:45 p.m. ET.
Aching to see the dazzling aurora displays that make up the northern lights, but can't get to the Arctic Circle to see them? Don't worry, a new Internet show has you covered.
The new web-based observatory AuroraMAX will go live tonight (Sept. 20) to broadcast real-time views of eye-catching northern lights, called the aurora borealis, as part of an outreach project by the Canadian Space Agency. [Amazing Aurora Photos]
"Armchair skywatchers everywhere can now discover the wonder of the northern lights live on their home computer screen," space agency chief Steve MacLean said in an announcement. "We hope that watching the dance of the northern lights will make you curious about the science of the sky and the relationship we have with our own star, the sun."
The Canadian Space Agency teamed up with the University of Calgary, the skywatching publication Astronomy North and the city of Yellowknife, which is about 318 miles (512 km) south of the Arctic Circle. According to the city's website, Yellowknife is "known for our outdoor recreation, midnight sun, aurora borealis and an unusual blend of northern culture."
The AuroraMAX website will include tips on how to observe auroras, explanations on why they occur, and highlight Canadian research into the relationship between the sun and Earth that leads to the dazzling sky shows. Photo galleries and videos of the phenomenon will also be included. A recap of each night will be broadcast on the following day.
Auroras occur when charged particles from the sun are funneled toward Earth by the planet's magnetic field and collide with the upper atmosphere near the poles. They are more active when the sun's activity peaks during its 11-year solar weather cycle. The sun is currently entering an active phase of its present cycle, so astronomers expect the northern lights to be more common and more dazzling over the next couple of years.
In addition to the aurora borealis in the north, the South Pole region also sees its own aurora displays, called the aurora australis.
In Canada, the peak of the aurora season typically runs from late August to May, because the nights are longer. The auroras themselves occur all year.
"The reason we classify August through May as the 'aurora watch' season is because of the extended number of 'dark' hours in Canada," aurora researcher Emma Spanswick of the University of Calgary told SPACE.com in an e-mail. "From an instrumentation perspective, the cameras we use to observe the aurora (like the AuroraMAX camera) are very sensitive. They are only able to operate when the sun is at least 12 degrees below the horizon … and in Northern Canada, that only happens between the months of August and May."
The AuroraMAX observatory will broadcast views of the northern lights through the sun's peak activity period, called solar maximum, which is expected in 2013, researchers said
Northern Lights Get Internet Reality Show
Buzz up!13 votes Share
retweet
EmailPrint..Tariq Malik
SPACE.com Managing Editor
SPACE.com tariq Malik
space.com Managing Editor
space.com – Mon Sep 20, 1:00 pm ET
This story was updated at 12:45 p.m. ET.
Aching to see the dazzling aurora displays that make up the northern lights, but can't get to the Arctic Circle to see them? Don't worry, a new Internet show has you covered.
The new web-based observatory AuroraMAX will go live tonight (Sept. 20) to broadcast real-time views of eye-catching northern lights, called the aurora borealis, as part of an outreach project by the Canadian Space Agency. [Amazing Aurora Photos]
"Armchair skywatchers everywhere can now discover the wonder of the northern lights live on their home computer screen," space agency chief Steve MacLean said in an announcement. "We hope that watching the dance of the northern lights will make you curious about the science of the sky and the relationship we have with our own star, the sun."
The Canadian Space Agency teamed up with the University of Calgary, the skywatching publication Astronomy North and the city of Yellowknife, which is about 318 miles (512 km) south of the Arctic Circle. According to the city's website, Yellowknife is "known for our outdoor recreation, midnight sun, aurora borealis and an unusual blend of northern culture."
The AuroraMAX website will include tips on how to observe auroras, explanations on why they occur, and highlight Canadian research into the relationship between the sun and Earth that leads to the dazzling sky shows. Photo galleries and videos of the phenomenon will also be included. A recap of each night will be broadcast on the following day.
Auroras occur when charged particles from the sun are funneled toward Earth by the planet's magnetic field and collide with the upper atmosphere near the poles. They are more active when the sun's activity peaks during its 11-year solar weather cycle. The sun is currently entering an active phase of its present cycle, so astronomers expect the northern lights to be more common and more dazzling over the next couple of years.
In addition to the aurora borealis in the north, the South Pole region also sees its own aurora displays, called the aurora australis.
In Canada, the peak of the aurora season typically runs from late August to May, because the nights are longer. The auroras themselves occur all year.
"The reason we classify August through May as the 'aurora watch' season is because of the extended number of 'dark' hours in Canada," aurora researcher Emma Spanswick of the University of Calgary told SPACE.com in an e-mail. "From an instrumentation perspective, the cameras we use to observe the aurora (like the AuroraMAX camera) are very sensitive. They are only able to operate when the sun is at least 12 degrees below the horizon … and in Northern Canada, that only happens between the months of August and May."
The AuroraMAX observatory will broadcast views of the northern lights through the sun's peak activity period, called solar maximum, which is expected in 2013, researchers said
Reminder: Rare Sky Show--Two Planets Align With Harvest Moon
From Yahoo:
Rare Sky Show: Two Planets Align with Harvest Moon
Buzz up! ..Geoff Gaherty
Starry Night Education
SPACE.com geoff Gaherty
starry Night Education
space.com – Tue Sep 21, 5:15 pm ET
Check out the eastern sky just after sunset tomorrow (Sept. 22), and you'll catch a skywatching treat. The nearly full moon will be rising just above the bright planet Jupiter and a somewhat dimmer Uranus.
You'll need binoculars if you hope to spot Uranus — it appears as a tiny bluish speck, too dim for the naked eye. So the coming celestial lineup is an excellent time to find that planet with binoculars or a small telescope, using Jupiter as a helpful guidepost.
This sky map shows where to spot the moon, Jupiter and Uranus this week.
Skywatching marathon
Several astronomical events happen in rapid succession this week, offering a celestial show for observers graced with clear skies. The times indicated here are for eastern North America and may vary a little if you’re elsewhere in the world:
Today (Sept. 21) at 8 p.m. EDT (1200 GMT), Jupiter is in opposition. This means that Jupiter will be exactly opposite the sun in Earth’s sky. This also means that Jupiter will be visible the entire night. (Yesterday — Sept. 20 — Jupiter made its closest approach to Earth in nearly 50 years.)
Five hours later, at 1 a.m. tomorrow (Sept. 22), Uranus will be in opposition, taking its turn opposite the sun in the sky.
Later tomorrow at 3 p.m., Jupiter and Uranus will be in conjunction, less than 1 degree apart in the sky. They won’t be visible right then in North America because they will be below the horizon, but they will still be close together when they rise just after sunset. You will be able to see both planets at the same time in the field of a small telescope at low magnification.
The show continues tomorrow night at 11:09 p.m. EDT (0309 GMT Thursday, Sept. 23), when the sun crosses the celestial equator — a projection of Earth's equator on the sky — and enters the southern hemisphere. This is known as the equinox, meaning "equal nights." Daytime and nighttime are of equal length, about 12 hours, everywhere on Earth. (Of course, the sun won’t be visible at this time in North America, being on the other side of the planet.)
Finally, at 5:17 a.m. EDT (0917 GMT) Thursday, the full moon of September will occur, since the moon will be exactly opposite the sun in the sky. This is a special full moon: It is the full moon closest to the equinox, known as the harvest moon. [Amazing Full Moon Photos]
So we have two planets and the moon directly opposite the sun within a two-day period. This means that all three will be grouped closely together in the sky.
When to see them
The best night to observe the moon, Jupiter and Uranus will be tomorrow, weather permitting.
The nearly full moon will rise around sunset, with Jupiter shining brightly beneath it. Uranus will be just slightly too faint to be seen with the naked eye, but will be easy to catch in binoculars or a small telescope.
This apparent close grouping of moon, Jupiter, and Uranus is actually a trick of perspective; the three objects aren’t anywhere near each other.
The moon is very close to Earth, about 251,000 miles (404,000 km or 0.003 astronomical units) away. One astronomical unit, or AU, is the distance between the Earth and sun, about 93 million miles (150 million km).
Jupiter is nearly1,500 times farther from Earth than the moon, placing it about 3.95 AU away. Uranus is nearly five times farther away than Jupiter, about 19.1 astronomical units from Earth.
One way to visualize the relative distances is to imagine that the Earth is at one end of a 100-yard football field and Uranus is at the other end.
On this scale, Jupiter would be on the 20-yard line, and the moon would be about half an inch from the end zone. In the "overhead" view of the planetary alignment, the innermost circle is Earth’s orbit; the moon’s orbit is too small even to be visible.
This explains why our tiny moon appears so large in the sky while the giant planets Jupiter and Uranus are mere pinpricks of light. The moon is just tons closer. Pure and simple.
Rare Sky Show: Two Planets Align with Harvest Moon
Buzz up! ..Geoff Gaherty
Starry Night Education
SPACE.com geoff Gaherty
starry Night Education
space.com – Tue Sep 21, 5:15 pm ET
Check out the eastern sky just after sunset tomorrow (Sept. 22), and you'll catch a skywatching treat. The nearly full moon will be rising just above the bright planet Jupiter and a somewhat dimmer Uranus.
You'll need binoculars if you hope to spot Uranus — it appears as a tiny bluish speck, too dim for the naked eye. So the coming celestial lineup is an excellent time to find that planet with binoculars or a small telescope, using Jupiter as a helpful guidepost.
This sky map shows where to spot the moon, Jupiter and Uranus this week.
Skywatching marathon
Several astronomical events happen in rapid succession this week, offering a celestial show for observers graced with clear skies. The times indicated here are for eastern North America and may vary a little if you’re elsewhere in the world:
Today (Sept. 21) at 8 p.m. EDT (1200 GMT), Jupiter is in opposition. This means that Jupiter will be exactly opposite the sun in Earth’s sky. This also means that Jupiter will be visible the entire night. (Yesterday — Sept. 20 — Jupiter made its closest approach to Earth in nearly 50 years.)
Five hours later, at 1 a.m. tomorrow (Sept. 22), Uranus will be in opposition, taking its turn opposite the sun in the sky.
Later tomorrow at 3 p.m., Jupiter and Uranus will be in conjunction, less than 1 degree apart in the sky. They won’t be visible right then in North America because they will be below the horizon, but they will still be close together when they rise just after sunset. You will be able to see both planets at the same time in the field of a small telescope at low magnification.
The show continues tomorrow night at 11:09 p.m. EDT (0309 GMT Thursday, Sept. 23), when the sun crosses the celestial equator — a projection of Earth's equator on the sky — and enters the southern hemisphere. This is known as the equinox, meaning "equal nights." Daytime and nighttime are of equal length, about 12 hours, everywhere on Earth. (Of course, the sun won’t be visible at this time in North America, being on the other side of the planet.)
Finally, at 5:17 a.m. EDT (0917 GMT) Thursday, the full moon of September will occur, since the moon will be exactly opposite the sun in the sky. This is a special full moon: It is the full moon closest to the equinox, known as the harvest moon. [Amazing Full Moon Photos]
So we have two planets and the moon directly opposite the sun within a two-day period. This means that all three will be grouped closely together in the sky.
When to see them
The best night to observe the moon, Jupiter and Uranus will be tomorrow, weather permitting.
The nearly full moon will rise around sunset, with Jupiter shining brightly beneath it. Uranus will be just slightly too faint to be seen with the naked eye, but will be easy to catch in binoculars or a small telescope.
This apparent close grouping of moon, Jupiter, and Uranus is actually a trick of perspective; the three objects aren’t anywhere near each other.
The moon is very close to Earth, about 251,000 miles (404,000 km or 0.003 astronomical units) away. One astronomical unit, or AU, is the distance between the Earth and sun, about 93 million miles (150 million km).
Jupiter is nearly1,500 times farther from Earth than the moon, placing it about 3.95 AU away. Uranus is nearly five times farther away than Jupiter, about 19.1 astronomical units from Earth.
One way to visualize the relative distances is to imagine that the Earth is at one end of a 100-yard football field and Uranus is at the other end.
On this scale, Jupiter would be on the 20-yard line, and the moon would be about half an inch from the end zone. In the "overhead" view of the planetary alignment, the innermost circle is Earth’s orbit; the moon’s orbit is too small even to be visible.
This explains why our tiny moon appears so large in the sky while the giant planets Jupiter and Uranus are mere pinpricks of light. The moon is just tons closer. Pure and simple.
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