From Science at NASA
NASA's Hubble Shows Milky Way is Destined for Head-On Collision
NASA astronomers announced Thursday they can now predict with certainty the next major cosmic event to affect our galaxy, sun, and solar system: the titanic collision of our Milky Way galaxy with the neighboring Andromeda galaxy.
The Milky Way is destined to get a major makeover during the encounter, which is predicted to happen four billion years from now. It is likely the sun will be flung into a new region of our galaxy, but our Earth and solar system are in no danger of being destroyed.
This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth's night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. (Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger)
"Our findings are statistically consistent with a head-on collision between the Andromeda galaxy and our Milky Way galaxy," said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore.
The solution came through painstaking NASA Hubble Space Telescope measurements of the motion of Andromeda, which also is known as M31. The galaxy is now 2.5 million light-years away, but it is inexorably falling toward the Milky Way under the mutual pull of gravity between the two galaxies and the invisible dark matter that surrounds them both.
"After nearly a century of speculation about the future destiny of Andromeda and our Milky Way, we at last have a clear picture of how events will unfold over the coming billions of years," said Sangmo Tony Sohn of STScI.
The scenario is like a baseball batter watching an oncoming fastball. Although Andromeda is approaching us more than 2,000 times faster, it will take 4 billion years before the strike.
Computer simulations derived from Hubble's data show that it will take an additional two billion years after the encounter for the interacting galaxies to completely merge under the tug of gravity and reshape into a single elliptical galaxy similar to the kind commonly seen in the local universe.
Although the galaxies will plow into each other, stars inside each galaxy are so far apart that they will not collide with other stars during the encounter. However, the stars will be thrown into different orbits around the new galactic center. Simulations show that our solar system will probably be tossed much farther from the galactic core than it is today.
To make matters more complicated, M31's small companion, the Triangulum galaxy, M33, will join in the collision and perhaps later merge with the M31/Milky Way pair. There is a small chance that M33 will hit the Milky Way first.
The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them. The Hubble Space Telescope's deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.
A century ago astronomers did not realize that M31 was a separate galaxy far beyond the stars of the Milky Way. Edwin Hubble measured its vast distance by uncovering a variable star that served as a "milepost marker."
Hubble went on to discover the expanding universe where galaxies are rushing away from us, but it has long been known that M31 is moving toward the Milky Way at about 250,000 miles per hour. That is fast enough to travel from here to the moon in one hour. The measurement was made using the Doppler effect, which is a change in frequency and wavelength of waves produced by a moving source relative to an observer, to measure how starlight in the galaxy has been compressed by Andromeda's motion toward us.
Previously, it was unknown whether the far-future encounter will be a miss, glancing blow, or head-on smashup. This depends on M31’s tangential motion. Until now, astronomers had not been able to measure M31's sideways motion in the sky, despite attempts dating back more than a century. The Hubble Space Telescope team, led by van der Marel, conducted extraordinarily precise observations of the sideways motion of M31 that remove any doubt that it is destined to collide and merge with the Milky Way.
"This was accomplished by repeatedly observing select regions of the galaxy over a five- to seven-year period," said Jay Anderson of STScI.
"In the worst-case-scenario simulation, M31 slams into the Milky Way head-on and the stars are all scattered into different orbits," said Gurtina Besla of Columbia University in New York, N.Y. "The stellar populations of both galaxies are jostled, and the Milky Way loses its flattened pancake shape with most of the stars on nearly circular orbits. The galaxies' cores merge, and the stars settle into randomized orbits to create an elliptical-shaped galaxy."
The space shuttle servicing missions to Hubble upgraded it with ever more-powerful cameras, which have given astronomers a long-enough time baseline to make the critical measurements needed to nail down M31's motion. The Hubble observations and the consequences of the merger are reported in three papers that will appear in an upcoming issue of the Astrophysical Journal.
For more images, video and information about M31's collision with the Milky Way, visit: http://hubblesite.org/news/2012/20
Transit of Venus -- Last One for 107 Years
Safe Observing Tips from Space dot Com
On Tuesday, June 5, skywatchers in North America will have their last chance to see Venus pass in front of the sun for over a century. Because of the International Date Line, this event will occur on Wednesday June 6 in Asia, Australia, Africa, and Europe.
This event, called a transit of Venus, is one of the rarest sights in astronomy. Transits of Venus occur in pairs 8 years apart, each pair separated from the next by over a century. The last pair occurred in 1881 and 1889, and the next pair will occur in 2117 and 2125. This week's transit is paired with a transit which occurred on June 8, 2004.
This graphic shows Venus position in its orbit on June 5, 2012, the day of the transit of Venus.
Why are transits of Venus so rare?
As the graphic associated with this guide shows, Venus' orbit is tilted by 3.4 degrees as compared to the Earth's orbit. As a result, most of the time Venus passes either above or below the sun when Venus is inferior conjunction with the sun (between the sun and Earth). Only when both Venus and Earth are at the points where the two orbits cross can we see Venus in front of the sun.
Venus transit observing safety
WARNING: It is always dangerous to stare directly at the sun!The sun's heat, when concentrated by your eye's lens on your eye's retina, can literally cook your sensitive retinal cells. The result can be a permanent blind spot in your eye. You only get one pair of eyes, so don't risk permanently damaging them.
There are only two safe ways to observe the transit of Venus
One way is to block the sun's damaging rays with a dense filter. The only safe filters are a #14 welder's glass, sold only by specialized welder's supply stores, or "eclipse shades": special glasses available only from telescope stores and astronomy clubs. Either of these cost less than a couple of dollars, so there's no excuse to endanger your eyes.
The only other safe way to observe the sun is with a "pinhole camera."
This can be made from a large cardboard box, such as a mover's "two-cube." Make a small hole in one end of the box, about a millimeter or two in diameter, which acts as the "lens," and place a white sheet of paper in the opposite end to serve as the viewing screen. Place the box over your head resting on your shoulders, and watch the transit on the screen.
Much simpler pinhole cameras can be improvised from any object with a small hole, but the advantage of using a large box is that it keeps stray light off the screen, allowing you to use a smaller pinhole, for a sharper image.
If you're observing with binoculars or a small telescope, there is no substitute for a proper full-aperture solar filter. Unless you block the sunlight from entering the telescope, you run the risk of concentrating the sun's light.
It was once common for solar observers to use their telescopes to project an image of the sun with an eyepiece. That was in the days when telescopes were made of metal and glass. Nowadays there is much plastic, and even cardboard, used in making telescopes and eyepieces, so that you run the risk of "meltdown" or even fire. It's just not safe.
The 2012 transit of Venus: How to watch
So, when is the best time to observe the transit?
In North America the best time will be in the hours before sunset on Tuesday afternoon. In Europe, Africa, and Australia, Venus will be in transit as the sun rises on Wednesday morning (June 6). In most of Asia and across the Pacific Ocean, any time during Wednesday should work. Detailed times are shown in the table accompanying this guide.
Astronomers chronicle Venus transits in terms of "contact." First contact is when Venus first touches the outer edge of the sun. Second contact is when Venus is first entirely on the sun. Similarly, third contact is when Venus touches the sun's edge from the inside, and fourth contact is when it is totally off the sun.
This chart shows the times of "contact" between Venus and the sun during the transit of Venus on June 5, 2012.
Transit Times for Major World Cities
What will you see?
For most observers, Venus will be a tiny round black disk, but large enough to be clearly visible with the unaided eye, properly protected by eclipse glasses or welder's glass. If you're viewing with a telescope, the most interesting times will be as Venus is entering or leaving the sun's disk.
One of the things to look for is the so-called "black drop" effect.
Here's an example: Hold up your thumb and forefinger in front of a bright background so that they are almost touching. You will see an interesting optical illusion whereby a black ligament appears to bridge the gap.
For the Venus transit, a similar illusion occurs just after second contact and just before third contact, when a dark ligament appears to join Venus to the dark sky. But is this entirely an optical illusion? Remember that Venus has a dense atmosphere which could contribute to this effect.
Many observers have reported seeing Venus as a bright ring just before it enters the sun's disk and just after it leaves. Mikhail Lomonosov, who organized the observations of the transits in the 1760s, correctly deduced from this that Venus had an atmosphere, illuminated from behind by the sun.
One difference between this transit and the one eight years ago is that many amateur astronomers now have telescopes which allow them to view the sun in hydrogen alpha light. It should be possible to see Venus silhouetted against prominences and the corona, before it moves in front of the chromosphere.
These are just a few of the interesting things which may be visible next Tuesday (or Wednesday, depending on your location). May you have clear skies, and don't forget to send us your images.
If you snap photos of the 2012 transit of Venus across the sun and would like to share them with SPACE.com, send images and comments to managing editor Tariq Malik at: email@example.com.
This article was provided to SPACE.com by Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu.
Venus transit 2012 - Live webcast
Free Live Venus transit Webcast from Bareket Observatory
2012 June 6th
A free, live webcast from Bareket Observatory in Israel will feature the Venus transit on June 6, 2012.
This relatively rare 'mini solar eclipse' -- meaning Venus will pass through the Earth's-Sun plane -- promises to be a truely unique astronomical event. A similar transit will not occur until 2117. This should be one of the most spectacular Venus transits in the last years!
This special webcast will took place from 02.33 - 04.56 UTC (GMT) June 15 - (05.33 - 07.56 Israel local time).
* For more information : visit the Live Venus transit page (you'll be automatically transfered to the live images, during the event):
http://www.bareket-astro.com/live-astronomical-we b-cast/live-free-venus-transit-webcast-6-june-2012 .html
Try your luck in real hands on Venus-transit experiments!
We invite you to discover the Sun and Venus during the transit using hands on Venus Transit activities.
Conduct your own science projects using the live transit feed !
Participants are invited to share the results of their projects on the website of partner Astronomers Without Borders or via their Facebook account at the live event web page.
For more information visit:
Astronomers without borders (AWB) website
Dragon Chases the ISS
DRAGON RENDEZVOUS: SpaceX's Dragon spacecraft will rendezvous with the International Space Station (ISS) on Friday, May 25th, making it the first commercial spacecraft to dock with the ISS. Last night, Dave Blanchard photographed the Dragon chasing the space station across the night sky over Flagstaff, Arizona:
"While the ISS was very bright and clearly visible in this image, the Dragon was very dim," says Blanchard. "It can be seen as a faint streak just below the ISS."
The two streaks will soon be joined. During the early hours of May 25th, the Dragon will approach the docking port on the station's Harmony module. Because this is the Dragon's first visit to the ISS, mission controllers will proceed with caution. A detailed series of navigation and communication tests will be performed before the capsule is allowed to move close enough for astronauts to grab it with the robot arm and connect it to the station.
After docking, the Dragon will remain connected for about three weeks, giving astronauts plenty of time to unload its 1200 lb of supplies and re-load it with used scientific equipment for return to Earth. Reversing the process of connecting the spacecraft to the station, astronauts will use the robotic arm to remove the capsule. The Dragon will then de-orbit and return to Earth under parachutes, splashing down in the Pacific Ocean off the California coast.
World's Largest Solar Eclipse Party
Hope you got to see it!
World's Largest Solar Eclipse Party Draws Thousands to Stadium
by Stephanie Pappas, Senior Writer
Date: 21 May 2012 Time: 12:34 AM ET
From: Space dot com
BOULDER, Colo. - Thousands of people turned their eyes to the sky at the University of Colorado's Folsom Field football stadium here Sunday (May 20) to watch the moon slip in front of the sun to create a spectacular "crescent sun."
The partial eclipse in Colorado occurred during a rare annular solar eclipse, in which the moon passed in front of — but did not completely obscure — the sun. In parts of China, Japan and eight western states, the celestial show created a dazzling "ring of fire" effect, while wide swathes of the U.S., including Colorado, saw a partial solar eclipse.
But even a partial eclipse was enough to draw a crowd of thousands to Folsom Field to see the moon take a bite from the sun. The organizers had billed the event as the world's largest solar eclipse viewing party.
At times, clouds periodically obscured the eclipsed sun, eliciting boos from the crowd. But when the clouds parted at 7:13 p.m. MDT (9:13 p.m. EDT/0113 GMT) several minutes before the maximum eclipse, it left some in the stadium speechless. [First Photos of May 20 Solar Eclipse]
"I can't think of words," said Bryce Pantoja, 15, who came with his family from the nearby city of Castle Rock to view the solar eclipse.
Astronomer Douglas Duncan, the director of the Fiske Planetarium at the University of Colorado, Boulder, arranged the eclipse-viewing event, mobilizing thousands of specialized solar-viewing glasses for the occasion. About 50,000 pairs of solar eclipse glasses were sold or given to schoolchildren in the days before the event, Duncan told SPACE.com.
There was no official count of the crowd at Folsom Field, but viewers likely numbered in the thousands and filled most of the upper deck of the stadium's eastern side. Duncan said the group was in the running for a world record of number of people viewing an eclipse at the same time. About 13,000 people were expected to attend the event.
The partial eclipse began at 6:22 p.m. MDT, reaching its maximum at 7:30 p.m., just 20 minutes before sunset.
The atmosphere in the stadium was alternately elated and disappointed as clouds turned eclipse-viewing into a game of hide-and-seek. Duncan and other astronomers entertained the crowd with raffles, astronomy tidbits and trivia during the slow creep of the moon's silhouette across the sun.
Twice, the astronomers instructed the crowd to stand up, face east and blow the clouds away — a tongue-in-cheek protest against the moody weather.
As the eclipse reached its maximum, clouds again moved in, leaving only portions of the sun visible. A chant of "move that cloud" rose up in the stadium. Shortly after the maximum, the crowd got an unobscured view of the waning eclipse. At sunset, pine trees on the mountainous horizon silhouetted against the parts of the sun left exposed.
"It's awesome," said Nathan Schneider, 12, of Boulder.
Schneider's father, Nicholas Schneider, is an astronomer at the University of Colorado, Boulder. Watching the eclipse through a pair of filtered binoculars, Schneider said that the show is only a warm-up for Aug. 21, 2017, when a total solar eclipse will be visible over most of North America.
"This is going to be beautiful," he said of the May 20 eclipse. "But a total solar eclipse is mind-blowing."
"Ring of Fire" Solar Eclipse
From Space (dot) com
Skywatchers in East Asia and the western United States should circle Sunday (May 20) on their calendars. That's when a solar eclipse will block out most of the sun, leaving a spectacular "ring of fire" shining in the sky for observers located along the eclipse's path.
The event is what's known as an annular solar eclipse — from the Latin "annulus," meaning "little ring" — and its full glory should be visible from much of Asia, the Pacific region and some of western North America, weather permitting. At its peak, the eclipse will block about 94 percent of the sun's light.
Other parts of the United States and Canada will still see a partial solar eclipse, without being treated to the ring of fire effect, though the East Coast will miss the event since the sun will have set before it begins. The eclipse will occur in the late afternoon or early evening of May 20 throughout North America, and May 21 for observers in Asia. Check out this eclipse skywatching guide to learn more about viewing locations and times.
Solar eclipses occur when the moon comes between Earth and the sun, casting a shadow on our planet. When the moon lines up perfectly with the sun and blots out all of its light, the result is a total eclipse. Partial eclipses cover only part of the sun's face.
Annular eclipses are similar to total eclipses in that the moon lines up with the sun dead-on. But in this case, the moon is close to apogee — the farthest point from Earth in its elliptical orbit around our planet — so it's a smidge too small in the sky to cover the solar disk completely. As a result, a ring of bright sunlight will still blaze around the moon's circumference.
Like other types of solar eclipses, annular eclipses are spectacular but potentially dangerous skywatching events. Care must be taken to observe them properly, or serious and permanent eye damage — including blindness — could result.
Warning: Never look directly at the sun, either with the naked eye or through telescopes or binoculars without the proper filters.
To safely observe the May 20 annular eclipse, you can buy special solar filters to fit over your equipment, or No. 14 welder's glass to wear over your eyes. Do NOT use standard sunglasses or any kind of homemade sun-shading contraption.
The safest and simplest technique is perhaps to watch the eclipse indirectly with the solar projection method. Use your telescope, or one side of your binoculars, to project a magnified image of the sun’s disk onto a shaded white piece of cardboard.
The image on the cardboard will be safe to view and photograph. Be sure to cover the telescope's finder scope or the unused half of the binoculars, however, and don't let anybody look through them.
And if you snap any good eclipse photos that you'd like to be considered for use in a story or gallery, send them to SPACE.com managing editor Tariq Malik at firstname.lastname@example.org.
The eta Aquarid Meteor Shower -- This weekend
The eta Aquarid
Global Notes: This shower can be seen from both hemispheres, but south is favored with twice as many meteors.
The 2010 eta Aquarid meteor shower peaks on May 6, 2012. The shower can be seen from both hemispheres, but the southern hemisphere is favored, receiving twice as many meteors as the north. Taking moonlight into account, forecasters estimate a maximum of 30+ visible meteors per hour. The best time to look, no matter where you live, is during the hours just before local sunrise.
Eta Aquarids are flakes of dust from Halley's Comet, which last visited Earth in 1986. Although the comet is now far away, beyond the orbit of Uranus, it left behind a stream of dust. Earth passes through the stream twice a year in May and October. In May we have the eta Aquarid meteor shower, in October the Orionids. Both are caused by Halley's Comet.
The shower is named after a 4th-magnitude star in the constellation Aquarius. The star has nothing to do with the meteor shower except that, coincidentally, meteors appear to emerge from a point nearby. Eta Aquarii is 156 light years from Earth and 44 times more luminous than the Sun.
The constellation Aquarius does not rise very far above the horizon in the northern hemisphere, and that's why northerners see relatively few meteors. But the ones they do see could be spectacular Earthgrazers. (continued below)
Sky maps: Northern Hemisphere | Southern Hemisphere
Earthgrazers are meteors that skim horizontally through the upper atmosphere. They are slow and dramatic, streaking far across the sky. The best time to look for Earthgrazers is between 2:00 to 2:30 a.m. local time when Aquarius is just peeking above the horizon.
Experienced meteor watchers suggest the following viewing strategy: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up somewhat toward the east. Meteors can appear in any part of the sky, although their trails will point back toward Aquarius.
Eta Aquarid meteoroids hit Earth's atmosphere traveling 66 km/s.
Typical eta Aquarid meteors are as bright as a 3rd magnitude star.
Biggest Full Moon of 2012!
From Space dot com
'Supermoon' Alert: Biggest Full Moon of 2012 Occurs This Week
by SPACE.com Staff
Date: 30 April 2012 Time: 01:54 PM ET
Skywatchers take note: The biggest full moon of the year is due to arrive this weekend.
The moon will officially become full Saturday (May 5) at 11:35 p.m. EDT. And because this month's full moon coincides with the moon's perigee — its closest approach to Earth — it will also be the year's biggest.
The moon will swing in 221,802 miles (356,955 kilometers) from our planet, offering skywatchers a spectacular view of an extra-big, extra-bright moon, nicknamed a supermoon.
And not only does the moon's perigee coincide with full moon this month, but this perigee will be the nearest to Earth of any this year, as the distance of the moon's close approach varies by about 3 percent, according to meteorologist Joe Rao, SPACE.com's skywatching columnist. This happens because the moon's orbit is not perfectly circular.
This month's full moon is due to be about 16 percent brighter than average. In contrast, later this year on Nov. 28, the full moon will coincide with apogee, the moon's farthest approach, offering a particularly small and dim full moon.
Though the unusual appearance of this month's full moon may be surprising to some, there's no reason for alarm, scientists warn. The slight distance difference isn't enough to cause any earthquakes or extreme tidal effects, experts say.
However, the normal tides around the world will be particularly high and low. At perigee, the moon will exert about 42 percent more tidal force than it will during its next apogee two weeks later, Rao said.
The last supermoon occurred in March 2011.
To view this weekend's supermoon to best effect, look for it just after it rises or before it sets, when it is close to the horizon. There, you can catch a view of the moon behind buildings or trees, an effect which produces an optical illusion, making the moon seem even larger than it really is.
Editor's note: If you'd like to share your supermoon photos for a possible story or gallery, send images and comments to SPACE.com managing editor Tariq Malik: email@example.com.