"The Sun's million mile-per-hour solar wind inflates a protective bubble, or heliosphere, around the solar system. It influences how things work here on Earth and even out at the boundary of our solar system where it meets the galaxy," says Dave McComas, Ulysses' solar wind instrument principal investigator and senior executive director at the Southwest Research Institute in San Antonio. "Ulysses data indicate the solar wind's global pressure is the lowest we have seen since the beginning of the space age."
The Sun's solar wind plasma is a stream of charged particles ejected from the Sun's upper atmosphere. The solar wind interacts with every planet in our solar system. It also defines the border between our solar system and interstellar space.
This border, called the heliopause, is a bubble-shaped boundary surrounding our solar system where the solar wind's strength is no longer great enough to push back the wind of other stars. The region around the heliopause also acts as a shield for our solar system, warding off a significant portion of the cosmic rays outside the galaxy.
"Galactic cosmic rays carry with them radiation from other parts of our galaxy," says Ed Smith, NASA's Ulysses project scientist at the Jet Propulsion Laboratory in Pasadena, California. "With the solar wind at an all-time low, there is an excellent chance the heliosphere will diminish in size and strength. If that occurs, more galactic cosmic rays will make it into the inner part of our solar system."
Galactic cosmic rays are of great interest to NASA. Cosmic rays are linked to engineering decisions for unmanned interplanetary spacecraft and exposure limits for astronauts traveling beyond low-Earth orbit.
In 2007, Ulysses made its third rapid scan of the solar wind and magnetic field from the Sun's south pole to the north pole. When the results were compared with observations from the previous solar cycle, the strength of the solar wind pressure and the magnetic field embedded in the solar wind was found to have decreased by 20 percent. The field strength near the spacecraft has decreased by 36 percent.
"The Sun cycles between periods of great activity and lesser activity," Smith says. "Right now, we are in a period of minimal activity that has stretched on longer than anyone anticipated."
Ulysses was the first mission to survey the space environment over the Sun's poles. Data from Ulysses have forever changed the way scientists view our star and its effects. The venerable spacecraft has lasted more than 17 years, or almost four times its expected mission lifetime.
The Ulysses solar wind findings were published in a recent edition of Geophysical Research Letters.
The Ulysses spacecraft was carried into Earth orbit aboard space shuttle Discovery on October 6, 1990. From Earth orbit it was propelled toward Jupiter, passing the planet on February 8, 1992. Jupiter's immense gravity bent the spacecraft's flight path downward and away from the plane of the planets' orbits. This placed Ulysses into a final orbit around the Sun that would take it over the north and south poles.
Sunday, September 28, 2008
Spacecraft discovers solar winds weakening
Thursday, August 28, 2008
Tuesday, August 19, 2008
Hubble unveils image of NGC 2074
In commemoration of the Hubble Space Telescope completing its 100,000th orbit around the Earth in its 18th year of exploration and discovery, scientists have aimed Hubble to take a snapshot of a dazzling region of celestial birth and renewal.
During Hubble's 100,000th orbit around the Earth it peered into a small portion of the nebula near the star cluster NGC 2074. The region is a firestorm of raw stellar creation, perhaps triggered by a nearby supernova explosion. It lies about 170,000 light-years away near the Tarantula nebula, one of the most active star-forming regions in our local group of galaxies.
The three-dimensional-looking image reveals dramatic ridges and valleys of dust, serpent-head "pillars of creation," and gaseous filaments glowing fiercely under torrential ultraviolet radiation. The region is on the edge of a dark molecular cloud that is an incubator for the birth of new stars.
The high-energy radiation blazing out from clusters of hot young stars already born in NGC 2074 is sculpting the wall of the nebula by slowly eroding it away. Another young cluster may be hidden beneath a circle of brilliant blue gas at the bottom center of the image.
In this approximately 100-light-year-wide fantasy-like landscape, dark towers of dust rise above a glowing wall of gases on the surface of the molecular cloud. The seahorse-shaped pillar at lower, right is approximately 20 light-years long, roughly four times the distance between our Sun and the nearest star, Alpha Centauri.
The region is in the Large Magellanic Cloud (LMC), a satellite of our Milky Way galaxy. It is a fascinating laboratory for observing star-formation regions and their evolution. Dwarf galaxies like the LMC are considered to be the primitive building blocks of larger galaxies.
Monday, August 18, 2008
M101
Messier 101 (M101, NGC 5457) was discovered by Pierre Méchain on March 27, 1781, and added as one of the last entries in Charles Messier's catalog. It was one of the first "spiral nebula" identified as such, in 1851 by William Parsons, the third Earl of Rosse.
Although extended 22 arc minutes on photos and quite bright, only the central region of this galaxy is visible in smaller telescopes, best at low powers. Suggestions of the spiral arms can be glimpsed in telescopes starting from 4 inch as nebulous patches. Several of these patches (i.e., spiral arm fragments) were assigned their own catalog numbers by William Herschel and later observers; according to the NGC and Burnham, there are 9 such numbers, 3 of which go back to Herschel who has found them on April 14, 1789, while the RNGC states that five of the others don't exist (ne); it mentions however that deVaucouleurs has them as knots: NGC 5447 (H III.787), 5449 (ne), 5450 (ne), 5451 (ne), 5453 (ne), 5455, 5458 (ne), 5461 (H III.788), 5462 (H III.789), and 5471.
On photographs, however, the Pinwheel Galaxy M101 is revealed as one of the most prominent Grand Design spirals in the sky. While quite symmetric visually and in very short exposures which show only the central region, it is of remarkable unsymmetry, its core being considerably displaced from the center of the disk. Halton Arp has included M101 as No. 26 in his Catalogue of Peculiar Galaxies as a "Spiral with One Heavy Arm".
M101 is the brightest of a group of at least 9 galaxies, called the M101 Group. The brightest companions are NGC 5474 (type Sc, 10.85 mag vis) to the SSE and NGC 5585 (Sa, 11.49 mag; Glyn Jones and Burnham misprinted this as 5485) to the NE. Other probable group members are NGC 5204 (Ir, 11.26), NGC 5238 (SB(d)m, 13.35p), NGC 5477 (Ir+, 13.8), UGC 8508 (Ir+, 14.5 p), Holmberg IV (UGC 8837, Ir+, 13.1 p), and UGC 9405.
The distance of M101 has been determined by the measurement of Cepheid variables with the Hubble Space Telescope in 1994/95 to be about 24 +/- 2 million light years, by the HST H0 Key Project Team (paper III, 1996). Kenneth Glyn Jones mentions earlier Earth-bound attempts of 1986, when two Cepheids were claimed to have been detected (yielding distance estimates between 20 and 26 million light years). It is also in good agreement with a distance determined from the Planetary Nebula Luminosity function, by Feldmeier, Ciardullo and Jacoby (1996) which is 25.1 +/- 1.6 million light years. According to the recent recalibration of the Cepheid distance scale, the "true" distance of M101 should be closer to a 10 percent higher value (27 million light years).
At the new distance from the HST and Hipparcos, it has a linear diameter of over 170,000 light years and is thus among the biggest disk galaxies, and its total apparent visual brightness of 7.9 mag corresponds to an absolute brightness of -21.6 magnitudes, or a luminosity of about 30 billion (3*10^10) times that of our sun.
Three supernovae have been discovered in M101: The first one, SN 1909A, appeared on January 26, 1909 and was discovered by Max Wolf; it was of peculiar type and reached mag 12.1 (Glyn Jones reports that the discovery took place in February, and the SN reached only mag 13.5). The second supernova 1951H was of type II, occurred in September 1951 and reached mag 17.5, while the third, SN 1970G, also type II, was discovered on July 30, 1970 by Michael Lovas, and reached mag 11.5. The remnant of Supernova 1970G was later detected in X-ray light and e.g. observed with the Chandra X-ray Observatory (CXO) satellite
Types of Stars and Star Groups
Everytime in the night sky when we look up we see the stars. But
- Do you know how many different types of stars are there?
- Do you know how many types of galaxies are there?
- Do you know that stars are of different colours?
So here is something to give a knowledge about the night sky....
Types of stars:-
1. Binary Stars
They are pairs of stars moving in orbit around their common centre of mass. They are also known as double stars. An optical pair appears to be double because two stars lie in the viewer's line of vision. Examples of double stars are Phakt in Columba and Arcus in Crux.
2. Black Dwarf
It is the remains of a dead white dwarf star after its heat is radiated into space.
3. Black Hole
It is what remains of a super collapsed star, whose gravitational pull is so great that no light can escape.
4. Brown Dwarf
It is a star whose mass is too small to have fusion occur at its core because the temperature and pressure there are too insufficient. It is also not very luminous.
5. Main-Sequence Stars
It is an ordinary star, one of about 90% of the stars that can be seen from Earth. It is much smaller than a giant star. It burns hydrogen into helium through nuclear fusion within itself. An example is our Sun.
6. Nebula
It is a cloud of gas or dust, and is considered to be the birthplace of a new star. There are three basic types: emission, reflection, and dark.
· An emission nebula glows brightly because its gas is energized by the stars formed within it. An example is the Orion Nebula.
· A reflection nebula is one in which sunlight reflects off the grains of dust within it. An example is the one which surrounds stars of the Pleides cluster.
· A dark nebula is a dense cloud of molecular hydrogen which absorbs light behind it. Examples are the Horsehead Nebula in Sagittarius and the Crab Nebula in Taurus.
7. Neutron Star
It is the tiniest star, having collapsed into a superdense state. It is thought to have formed when a large star exploded as a supernova.
8. Nova
It is a star that brightens suddenly, lasts a few days, fades away, and returns to its normal state.
9. Pulsar
It is a rapidly spinning neutron star that emits pulses of energy.
10. Quasar
It is a quasistellar object, very far away and very bright. It gives off more energy than one hundred giant galaxies.
11. Red Giant
It is a large, bright star, many times larger than the Sun, but with a cool surface. It is believed to be in the end stage of its life cycle. Examples are Aldebaran in Taurus and Ras Algethi in Hercules.
12. Supergiant
It is the largest and most luminous type of star, being a dying star. It has used up its hydrogen fuel and has begun to expand and cool. Examples are Antares in Scorpius and Betelgeuse in Orion.
13. Supernova
It is an exploding supergiant, being the death of a star. The Crab Nebula was formed by a supernova.
14. Variable Star
It is a star whose brightness changes. This is usually caused by pulsations within it. Examples of variable stars are Polaris in Ursa Minor (Cepheid) and R Centauri in Centaurus (Mira).
15. White Dwarf
It is a very dense, small, hot star in the last stage of its life. It occurs when a red giant sheds its outer layers as a planetary nebula. The electrons and protons have been packed as closely as possible by gravity. An example of the white dwarf is the Pup, companion star of Sirius in Canis major.
16. Wolf-Rayet Star
It is a hot, luminous star that is rapidly losing mass in a wind. It represents a late stage in the life of massive stars.
Types of galaxies:-
Galaxy:- It is a system of stars, dust, and gas held together by gravity. There are three basic types: spiral, elliptical, and irregular. ·
- A spiral galaxy is a flattened, discus-shaped collection of stars, having a central bulge. Examples include the Milky Way and Andromeda. ·
- An elliptical galaxy ranges in shape from a sphere to a flattened globe. Examples include the Sagittarius Dwarf and M31. ·
- An irregular galaxy has no pattern of shape. Examples include the Large Magellanic Cloud and the Small Magellanic Cloud.
Types of colours of different stars : -
Star Colours :- They are, in descending order of temperature, greenish, blue, blue-white, yellowish-white, yellow, orange-yellow, orange-red, red, infrared.
NASA SCIENTISTS GET FIRST IMAGES OF EARTHLY FLYBY AESTROID :
"With these first radar observations finished, we can guarantee that next week's 1.4-lunar-distance approach is the closest until at least the end of the next century," says Steve Ostro, JPL astronomer and principal investigator for the project. "It is also the asteroid's closest Earth approach for more than 2,000 years."
Scientists at NASA's Near-Earth Object Program Office at JPL have determined that there is no possibility of an impact with Earth in the foreseeable future.
Asteroid 2007 TU24 was discovered by the NASA-sponsored Catalina Sky Survey on October 11, 2007. The first radar detection of the asteroid was acquired on January 23 using the Goldstone 230-foot (70-meter) antenna. The Goldstone antenna is part of NASA's Deep Space Network Goldstone station in Southern California's Mojave Desert. Goldstone's 230-foot (70-meter diameter) antenna is capable of tracking a spacecraft traveling more than 10 billion miles (16 billion kilometers) from Earth. The surface of the 230-foot reflector must remain accurate within a fraction of the signal wavelength, meaning that the precision across the 41,400-square-foot (3,850-square-meter) surface is maintained within 0.4 inch (1 centimeter).
Ostro and his team plan further radar observations of asteroid 2007 TU24 using the National Science Foundation's Arecibo Observatory in Puerto Rico on January 27-28
and February 1-4.
The asteroid will reach an approximate apparent magnitude 10.3 on January 29-30 before quickly becoming fainter as it moves farther from Earth. On that night, the asteroid will be observable in dark and clear skies through amateur telescopes with apertures of at least 3 inches (7.6 centimeters). An object with a magnitude of 10.3 is about 50 times fainter than an object just visible to the naked eye in a clear, dark sky.
NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to our planet.
New Planet found in Leo
Most of the 280 or so planets discovered to date are gas giants similar to Jupiter, although some with masses below 10 times that of the Earth have already been found. Planets with masses of between one and 10 times the Earth are often dubbed super-Earths. In this case, current models predict that the new planet is a rocky type and has a radius some 50 percent larger than the Earth.
