Courtesy NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. MellingerI think this is really interesting - below is straight from a release from NASA.
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.
"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 two thousand 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. "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.
NASA will attempt to revive the $2 billion Hubble Space Telescope on Wednesday, officials say. The telescope was idled two weeks ago by an equipment failure.
Google Sky now works in a web browser (without a download). From within a web browser one can navigate the sky in a way similar to using Google Maps. Zoom or drag your way through a universe of stitched together images from telescopes and satellites. Try it out. It is lots of fun.
To get started on your own outer-space adventure, download the most recent version of Google Earth software. Select "Switch to Sky" under the "view" menu or click on the icon that I show with a red arrow.
The Universe is a big place so you might get lost. For help, the column on the left offer lots of guided tours. Try the sightseeing link under places. The screen capture shows what I found by selecting "Supernovae and Exotic Stars" under the layers section. PCworld has created a file of Google Sky Placemarks. Download it and open it with Google Earth. In the left column, in the Places box, click the (+) next to "Spectacular Sights in Google Sky". These are like bookmarks (or stick pins) that take you to some fantastic places. One (A Dramatic Outburst - V838Mon) has a time line slider so you can see how the event changed over several years.
Google sky incorporates high-resolution images from NASA's Hubble Space Telescope, the Space Telescope Science Institute, the Sloan Digital Sky Survey, and the Digital Sky Survey Consortium into a fun, interactive learning tool. I hope you can check it out (high speed internet required).
Scientists have unexpectedly discovered new evidence of dark matter revealing itself in the form of a ghostly ring arising from the collision of two galaxy clusters.
Because it neither reflects nor produces light, dark matter is invisible. Yet it is the most abundant material in the universe. Its presence can only be detected indirectly by its effect on visible matter, such as via “gravitational lensing”, in which the gravitational force of a nearer object (such as a star) or material (such as dark matter) bends the light coming from more distant background objects.
"The collision between the two galaxy clusters created a ripple of dark matter that left distinct footprints in the shapes of the background galaxies," said M. James Jee of Johns Hopkins University in Baltimore, Md., a member of the team of Hubble astronomers that located the dark-matter ring.
The ripple is humongous, measuring 2.6 million light-years across. The scientists discovered it while mapping the distribution of dark matter within the galaxy cluster Cl 0024+17 (ZwCl 0024+1652), located 5 billion light-years from Earth.
"It's like looking at the pebbles on the bottom of a pond with ripples on the surface. The pebbles' shapes appear to change as the ripples pass over them. So, too, the background galaxies behind the ring show coherent changes in their shapes due to the presence of the dense ring."
Luckily for Jee and his team the galactic collision took place right in Earth’s line of sight, and from that head-on view gives the dark matter a ring shape.
"This is the first time we have detected dark matter as having a unique structure that is different from both the gas and galaxies in the cluster," Jee said.
The Space Telescope Science Institute (the Hubble Space Telescope's science home), is conducting a three-day workshop beginning November 28 that will feature a roster of scientists, engineers, and astronauts presenting their thoughts about what NASA's return of human presence to the Moon could mean for astrophysics.
You can see the presentations live, or view previous webcasts from the presentations, by visiting the Space Telescope Science Institute’s webcast page.
As someone who is fascinated by space, the Hubble Space Telescope is something that I think is not only cool, but also essential to our learning about the universe we live in. That’s why this summer I was bummed to learn that NASA had decided to let the telescope fail in the coming years and then crash it into the ocean. I was happy to learn a few weeks ago that NASA has now announced that it will send a space shuttle crew to service and upgrade the telescope to make it functional through 2013. The service mission will add two new instruments to the telescope, allowing for even better observations than before.
Hubble was designed to be upgraded while in orbit – and it has had four service missions since its launch in 1990. Each service mission has improved the performance of the telescope and the images and data it sends to scientists and researchers.
This fifth servicing mission will include regular maintenance such as installing new gyroscopes and new batteries, and also the installation of two new instruments, the Cosmic Origins Spectrograph (COS) and the Wide Field Camera 3 (WFC3).
According to NASA,
COS will measure the structure and composition of the ordinary matter concentrated in the "cosmic web," long, narrow filaments of galaxies and intergalactic gas separated by huge voids. COS will use faint distant quasars as "cosmic flashlights," whose beams of light pass through the cosmic web. Absorption of this light by "stuff" in the web reveals characteristics of that material. This allows scientists to determine its composition and its specific location in space. These observations, covering vast distances across space and time, will illuminate both the large-scale structure of the universe and the progressive changes in chemical composition of matter as the universe has grown older.
The WFC3 will extend Hubble's capability to see deep into the universe, with the power to observe in multiple wavelengths (colors) of light including infrared, visible and ultraviolet light. WFC3 can, for example, observe young, hot stars that glow predominantly in ultraviolet and older, cooler stars that glow predominantly in infrared in the same galaxy. The first stars and galaxies to form in the universe are so old and distant that their light is now relegated to infrared wavelengths.
Other scheduled work includes installing a refurbished Fine Guidance Sensor, as well as attempting to repair the Space Telescope Imaging Spectrograph. Installed in 1997, it stopped working in 2004.
The [Space Telescope Imaging Spectrograph] is used for high resolution studies in visible and ultraviolet light of both nearby star systems and distant galaxies, providing information about the motions and chemical makeup of stars, planetary atmospheres, and other galaxies.
The service mission is tentatively scheduled for 2008.
Will NASA find the risks of a repair mission to fix the Hubble telescope acceptable? A rehab mission would keep Hubble working until about 2013. NASA will give its answer Tuesday.
The Hubble constant, formulated by Edwin Hubble in 1929, has remained fairly constant since the 1950's. Kris Stanek, associate professor of astronomy at Ohio State, and his coauthors are publishing a paper that may change the accepted value of the Hubble constant and also the accepted size and age of the universe.
They studied two of the brightest stars in M33, which are part of a binary system, meaning that the stars orbit each other. As seen from Earth, one star eclipses the other every five days.
They measured the mass of the stars, which told them how bright those stars would appear if they were nearby. But the stars actually appear dimmer because they are far away. The difference between the intrinsic brightness and the apparent brightness told them how far away the stars were -- in a single calculation.
To their surprise, the distance was 15 percent farther than they expected: about 3 million light-years away, instead of 2.6 million light-years as determined by the Hubble constant.
This new method took 10 years to develop. To make such a drastic change to the accepted view of the universe will require additional experimentation.
"Our margin of error is now 6 percent, which is actually pretty good," Stanek said. Next, they may do the same calculation for another star system in M33, to reduce their error further, or they may look at the nearby Andromeda galaxy. The kind of binary systems they are looking for are relatively rare, he said, and getting all the necessary measurements to repeat the calculation would probably take at least another two years.
Soure article: Ohio State University Research Archive