Edwin Hubble

Edwin Powell Hubble (November 20, 1889 - September 28, 1953) was an American astronomer, noted for his discovery of galaxies beyond the Milky Way and the cosmological redshift.

Edwin Hubble was one of the leading astronomers of modern times and laid down the foundation upon which physical cosmology now rests.

Hubble's observations in 1923–1924 with the Hooker Telescope established beyond doubt that the fuzzy "nebulae" seen earlier with less sensitive telescopes were not part of our galaxy, as had been thought, but were galaxies themselves, outside the Milky Way.

He announced this discovery on January 1, 1925. Hubble also devised a classification system for galaxies, grouping them according to their content, distance, shape, size and brightness.

Hubble was generally incorrectly credited with discovering the redshift of galaxies..

For more information about the topic Edwin Hubble, read the full article at Wikipedia.org, or see the following related articles:

Cepheid variable

A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute luminosity.

Since the period-luminosity relation can be calibrated with great precision using the nearest Cepheid stars, the distances found with this method are among the most accurate available..

For more information about the topic Cepheid variable, read the full article at Wikipedia.org, or see the following related articles:

Supergiant — Supergiants are the most massive stars. Supergiants can have masses from 10 to 70 solar masses and brightness from 30,000 up to hundreds of thousands ... > read more

Red giant — A red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... > read more

Luminosity — In general physics, luminosity (more properly called luminance) is the density of luminous intensity in a given ... > read more

Star cluster — Star clusters are groups of stars which are gravitationally bound. Two distinct types of star cluster can be distinguished: globular clusters are ... > read more

Supergiant

Supergiants are the most massive stars.

Supergiants can have masses from 10 to 70 solar masses and brightness from 30,000 up to hundreds of thousands times the solar luminosity.

They vary greatly in radii, usually from 30 to 500, or even in excess of 1000 solar radii.

Because of their extreme masses they have short lifespans of only 10 to 50 million years and are only observed in young cosmic structures such as open clusters, the arms of spiral galaxies, and in irregular galaxies.

They are less abundant in spiral galaxy bulges, and are not observed in elliptical galaxies, or globular clusters, all of which are believed to be composed of old stars.

Currently, the largest known stars in terms of physical size, not mass or luminosity, are the supergiants VV Cephei, V354 Cephei, KW Sagitarii, KY Cygni, and the Garnet Star..

For more information about the topic Supergiant, read the full article at Wikipedia.org, or see the following related articles:

Blue supergiant star — Blue supergiants are supergiant stars (class I) of spectral type O. They are extremely hot and bright, with surface temperatures of between 20,000 - ... > read more

Red supergiant star — Red supergiants are supergiant stars of spectral type K-M and a luminosity class of I. They are the largest stars in the universe in terms of ... > read more

Red giant — A red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... > read more

Stellar classification — In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral ... > read more

Supernovae Not What They Used To Be; Distant Supernovae Distinctly Brighter

Using the NASA/ESA Hubble Space Telescope, astronomers pinpointed a blaze of light from the farthest supernova ever seen, SN 1997ff -- a dying star that exploded 10 billion years ago. (Credit: NASA/ESA, Adam Riess (Space Telescope Science Institute))

(Oct. 24, 2007) — Exploding stars that light the way for research on dark energy aren’t as powerful or bright, on average, as they once were, says a new study by University of Toronto astronomers.

The study, which compared supernovae in nearby galaxies with those that exploded up to nine billion light years away in the distant universe, found the distant supernovae were an average of 12 per cent brighter. The distant supernovae were brighter because they were younger, the study found.

Since uniformly bright exploding stars help astronomers study the nature of dark energy – an unknown type of energy that causes the universe to accelerate its expansion – the team’s findings suggest it could become more difficult to study dark energy in the future. Astronomers can correct for supernovae of varying brightness, but it will prove challenging.

“The findings do not call into question that the universe is accelerating but the evolving mix of supernovae could limit future attempts to determine the nature of dark energy,” said Andrew Howell, lead author of the study and post-doctoral researcher.

“You can think of supernovae as light bulbs,” he said. “We found that the early universe supernovae had a higher wattage, but as long as we can figure out the wattage, we should be able to correct for that. Learning more about dark energy is going to take very precise corrections though and we aren’t sure how well we can do that yet.”

The paper, Predicted and Observed Evolution in the Mean Properties of Type Ia Supernovae with Redshift, was co-authored by post-doctoral researchers Mark Sullivan and Alex Conley and Professor Ray Carlberg of astronomy and astrophysics. It appears in the Sept. 20 issue of the Astrophysical Journal Letters.

Adapted from materials provided by University Of Toronto.

Massive Star's Afterlife: A Supernova Seeds New Planets

G292.0+1.8 is a young supernova remnant located in our galaxy. This deep Chandra image shows a spectacularly detailed, rapidly expanding shell of gas that is 36 light years across and contains large amounts of oxygen, neon, magnesium, silicon and sulfur. Supernovas are of great interest because they are a primary source of the heavy elements believed to be necessary to form planets and life. (Credit: X-ray: NASA/CXC/Penn State/S. Park et al. Optical: Palomar/DSS)

(Oct. 24, 2007) — A spectacular new image shows how complex a star's afterlife can be. By studying the details of this image made from a long observation by NASA's Chandra X-ray Observatory, astronomers can better understand how some stars die and disperse elements like oxygen into the next generation of stars and planets.

At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. The image shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen, other elements such as neon and silicon that were forged in the star before it exploded.

"We are finding that, just like snowflakes, each supernova remnant is complicated and beautiful in its own way," said Sangwook Park of Penn State who led the work, released in conjunction with the "8 Years of Chandra" symposium in Huntsville, Ala.

By mapping the distribution of X-rays in different energy bands, the Chandra image traces the distribution of chemical elements ejected in the supernova. The results imply that the explosion was not symmetrical. For example, blue (silicon and sulfur) and green (magnesium) are seen strongly in the upper right, while yellow and orange (oxygen) dominate the lower left. These elements light up at different temperatures, indicating that the temperature is higher in the upper right portion of G292.0+1.8.

Slightly below and to the left of the center of G292.0+1.8 is a pulsar, a dense, rapidly rotating neutron star that remained behind after the original star exploded. Assuming that the pulsar was born at the center of the remnant, it is thought that recoil from the lopsided explosion may have kicked the pulsar in this direction.

Surrounding the pulsar is a so-called pulsar wind nebula, a magnetized bubble of high-energy particles. The narrow, jet-like feature running from north to south in the image is likely parallel to the spin axis of the pulsar. This structure is most easily seen in high energy X-rays. In the case of G292.0+1.8, the spin direction and the kick direction do not appear to be aligned, in contrast to apparent spin-kick alignments in some other supernova remnants.

Another intriguing feature of this remnant is the bright equatorial belt of X-ray emission that extends across the center of the remnant. This structure is thought to have been created when the star - before it died - expelled material from around its equator via winds. The orientation of the equatorial belt suggests that the parent star maintained the same spin axis both before and after it exploded.

"The detection of the pulsar and its wind nebula confirms that the supernova that led to G292 produced a neutron star through the collapse of the core of a massive star," said coauthor John Hughes of Rutgers University, "The ability to study the asymmetry of the original explosion using X-ray images of the remnant gives us a powerful new technique for learning about these cataclysmic events."

These results will appear in the December 1st issue of The Astrophysical Journal Letters.

Adapted from materials provided by Chandra X-ray Center.

Solar Telescope Soars Into Sky On Jumbo-jet-sized Balloon

Slender hoses, blown into arcs by the wind, partially fill
theballoon with helium before launch. A large portion of
the balloon is left unfilled so it can expand as it ascends into the
stratosphere, where air pressure is considerably lower.
(Credit: Photo by Carlye Calvin, Copyright UCAR)

(Oct. 24, 2007) — In a landmark test flight, the National Center for Atmospheric Research (NCAR) and a team of research partners this month successfully launched a solar telescope to an altitude of 120,000 feet, borne by a balloon larger than a Boeing 747 jumbo jet. The test clears the way for long-duration polar balloon flights beginning in 2009 that will capture unprecedented details of the Sun's surface.

"This unique research project will enable us to view features of the Sun that we've never seen before," says Michael Knölker, director of NCAR's High Altitude Observatory and a principal investigator on the project. "We hope to unlock important mysteries about the Sun's magnetic field structures, which at times can cause electromagnetic storms in our upper atmosphere and may have an impact on Earth's climate."

The project, known as Sunrise, is an international collaboration involving NCAR, NASA, Germany's Max Planck Institute for Solar System Research and Kiepenheuer Institute for Solar Physics, Spain's Astrophysics Institute of the Canary Islands, and the Swedish Space Corporation. Additional U.S. partners include the Lockheed Martin Corporation and the University of Chicago. Funding for NCAR's work on the project comes from NASA and from the National Science Foundation, which is NCAR's primary sponsor.

The project may usher in a new generation of balloon-borne scientific missions that cost less than sending instruments into space. Scientists also can test an instrument on a balloon before making a commitment to launch it on a rocket.

The balloon, with its gondola of scientific instruments, was launched successfully on the morning of October 3 from the Columbia Scientific Balloon Facility in Fort Sumner, New Mexico. It flew for about 10 hours, capturing stable images of the solar surface and additional data from the various instruments of the sophisticated payload. The gondola then separated from the balloon and descended with a parachute, landing safely in a field outside Dalhart, Texas.

"We were able to verify the workings of the entire system end to end," says David Elmore, an NCAR engineer who oversaw the test flight. "We can now move on to planning the first full-scale mission with confidence."

Observing the midnight Sun

The ultimate goal of the Sunrise project is to investigate the structure and dynamics of the Sun's magnetic fields. The fields fuel solar activity, including plasma storms that buffet Earth's outer atmosphere and affect sensitive telecommunications and power systems. The fields also cause variations in solar radiation, which may be significant factors in long-term changes in Earth's climate.

The Sunrise project is scheduled next for a multiday flight over the Arctic in the summer of 2009, launching from Kiruna, Sweden. By taking advantage of the midnight Sun, the telescope will be able to capture continuous images for a period of several days to as long as two weeks, possibly orbiting the Arctic. It may be launched later on another long-distance flight over the Arctic or the Antarctic.

At an altitude of 120,000 feet, the telescope will rise above most of the turbulence of the atmosphere and ultraviolet-absorbing water vapor and ozone. It will be able to view stable images in the ultraviolet range, which allow for higher resolution than can be obtained from Earth's surface.

The telescope will capture features on the solar surface as small as 30 kilometers across (about 19 miles), more than double the resolution achieved by any other instrument to date. This will enable scientists to examine structures on the Sun that are believed to be key to understanding the mechanisms driving solar activity. In addition, by observing the same area during an entire flight over high latitudes in summer, the telescope will enable scientists to continually witness changes in the magnetic fields without the interruption of night.

The Sunrise project has presented engineers with a number of extraordinary challenges. The balloon is designed to carry 6,000 pounds of equipment, including a 1-meter (39-inch) solar telescope, additional observing instruments, communications equipment, computers and disk drives, solar panels, and roll cages and crush pads to protect the payload on landing. The equipment must be able to withstand dramatic changes in temperature, and the steel and aluminum gondola cannot vibrate in ways that could interfere with the operation of the telescope.

One of the most difficult aspects of the engineering work was to design the gondola in such a way that the telescope in flight would remain focused on a specific and relatively tiny area of the Sun, even while twisting on a soaring balloon for a week or longer during the full-scale research missions. To accomplish this, the gondola includes both a torque motor drive to keep the gondola and telescope in the correct orientation and a precision guiding and compensation system to constantly correct the telescope's aim.

In addition to the telescope, the gondola on its full-scale research missions will carry a polarimetric spectrograph that will measure wavelengths in the Sun's electromagnetic spectrum and enable scientists to make inferences about its magnetic fields. Another instrument, known as an imaging magnetograph, will provide two-dimensional magnetic field maps.

Because the gondola is designed to withstand considerable force when it lands, the instruments can be launched on repeated missions.

"This is a very economical way of rising above the atmosphere and capturing images that cannot be captured from Earth," Knölker says. "What we are doing is laying the groundwork for the next generation of space flights."

Adapted from materials provided by National Center for Atmospheric Research.

China And ESA Launch Moon Mission -- Chang'e-1

Artist's impression of SMART-1 . SMART-1 is Europe's first mission to the Moon. (Credit: ESA)

(Oct. 25, 2007) — A bold new mission to the Moon was launched by the Chinese National Space Administration (CNSA). Chang’e-1 blasted off from the Xichang Satellite Launch Centre, Sichuan, atop a Long March 3A rocket on October 24, 2007.

Chang’e-1 represents the first step in the Chinese ambition to land robotic explorers on the Moon before 2020.

Chang’e-1 has four mission goals to accomplish. The first is to make three-dimensional images of many lunar landforms and outline maps of major lunar geological structures. This mapping will include the first detailed images taken of some regions near the lunar poles.

Chang’e-1 is also designed to analyze the abundance of up to 14 chemical elements and their distribution across the lunar surface. Thirdly it will measure the depth of the lunar soil and lastly it will explore the space weather between the Earth and the Moon.

The spacecraft is large, weighing in at 2350 kg and it will operate from a low, circular lunar orbit, just 200 km above the surface of the Moon. From here, it will perform its science mission for a full year.

ESA is collaborating with the Chinese on this mission by providing spacecraft and ground operations support services to CNSA. The two agencies will also share data and encourage a visitors’ programme so that researchers can learn from each other.

During ESA’s SMART-1 mission, the Agency provided the Chinese with details of the spacecraft's position and transmission frequencies, so that the Chinese could test their tracking stations and ground operations by following it. This was part of their preparation for Chang’e-1. Now it is time for Chang’e-1 itself to fly.

Hermann Opgenoorth, Head of ESA’s Solar System Missions Division says, “Participation in Chang’e-1 gives European scientists and ESA experts a welcome opportunity to maintain and pass on their expertise and to continue their scientific work. Based on the experience gained with this first mission, we intended to cooperate on the next missions in China's Chang’e line of lunar explorers.”

To perform its science mission, Chang’e-1 carries a variety of instruments: a CCD stereo camera, a laser altimeter, an imaging interferometer, a gamma-ray/X-ray spectrometer, a microwave radiometer, a high-energy particle detector, and a solar wind particle detector.

Named after the Chinese goddess of the Moon, Chang’e-1 represents the first phase in the Chinese Lunar Exploration Programme (CLEP). This programme is expected to last until around 2020 and the next phase will include a lander and associated rover. Looking farther into the future, plans are being drawn up for a sample return mission to bring lunar rocks to Earth for analysis.

"ESA's expertise in tracking Chang'e-1 sets the stage for future cooperation with China. The Agency's tracking station network, ESTRACK, is a resource that benefits not only the Agency but also all space science through such international cooperation," said Erik Soerensen, Head of the System Requirements and Validation Section at ESA's European Space Operations Centre.

Adapted from materials provided by European Space Agency.