central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years. The nebula's complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.
There is something very unusual in this picture of the Earth -- can you find it? A fleeting phenomenon once thought to be only a legend has been newly caught if you know just where to look. The above image was taken from the orbiting International Space Station (ISS) in late April and shows familiar ISS solar panels on the far left and part of a robotic arm to the
far right. The rarely imaged phenomenon is known as a red sprite and it can be seen, albeit faintly, just over the bright area on the image right. This bright area and the red sprite are different types of lightning, with the white flash the more typical type. Although sprites have been reported anecdotally for as long as 300 years, they were first caught on film in 1989 -- by accident. Much remains unknown about sprites including how they occur, their effect on the atmospheric global electric circuit, and if they are somehow related to other upper atmospheric lightning phenomena such as blue jets or terrestrial gamma flashes.
A rare and spectacular head-on collision between two galaxies appears in this Hubble telescope picture of the Cartwheel Galaxy, located 500 million light-years from Earth in the constellation Sculptor.
The striking ring-like feature is a direct result of a smaller intruder galaxy — possibly one of two objects to the right of the ring — that careened through the core [close-up i
mage at lower left] of the host galaxy. Like a rock tossed into a lake, the collision sent a ripple of energy into space, plowing gas and dust in front of it. Expanding at 200,000 mph, this cosmic tsunami leaves in its wake a firestorm of new star creation. Hubble resolves bright blue knots that are gigantic clusters of newborn stars [close-up image at upper left] and immense loops and bubbles blown into space by exploding stars (called supernovae) going off like a string of firecrackers.
The Cartwheel Galaxy (also known as ESO 350-40) is a lenticular galaxy about 500 million light-years away in the constellation Sculptor. It is an estimated 150,000 light-years across, has a mass of about 2.9–4.8 × 109 solar masses, and rotates at 217 km/s.
It was discovered by Fritz Zwicky in 1941. Zwicky considered his discovery to be "one of the most complicated structures awaiting its explanation on the basis of stellar dynamics."
An estimation of the galaxy's span resulted in a conclusion of 150,000 light years, which is slightly larger than the Milky Way.
Evolution
The galaxy was once a normal spiral galaxy before it apparently underwent a head-on collision with a smaller companion approximately 200 million years ago (i.e., 200 million years prior to the image) When the nearby galaxy passed through the Cartwheel Galaxy, the force of the collision caused a powerful shock wave through the galaxy, like a rock being tossed into a sandbed. Moving at high speed, the shock wave swept up gas and dust, creating a starburst around the galaxy's center portion that were unscathed. This explains the bluish ring around the center, brighter portion.[9] It can be seen that the galaxy is beginning to retake the form of a normal spiral galaxy, with arms spreading out from a central core.
Alternatively, a model based on the gravitational Jeans instability of both axisymmetric (radial) and nonaxisymmetric (spiral) small-amplitude gravity perturbations allows an association between growing clumps of matter and the gravitationally unstable axisymmetric and nonaxisymmetric waves which take on the appearance of a ring and spokes.
X-ray sources
The unusual shape of the Cartwheel Galaxy may be due to a collision with a smaller galaxy such as those in the lower left of the image. The most recent star burst (star formation due to compression waves) has lit up the Cartwheel rim, which has a diameter larger than the Milky Way. Star formation via starburst galaxies, such as the Cartwheel Galaxy, results in the formation of large and extremely luminous stars. When massive stars explode as supernovas, they leave behind neutron stars and black holes. Some of these neutron stars and black holes have nearby companion stars, and become powerful sources of X-rays as they pull matter off their companions. The brightest X-ray sources are likely black holes with companion stars, and appear as the white dots that lie along the rim of the X-ray image. The Cartwheel contains an exceptionally large number of these black hole binary X-ray sources, because many massive stars formed in the rim.
The Cartwheel Galaxy (also known as ESO 350-40) is a lenticular galaxy about 500 million light-years away in the constellation Sculptor. It is an estimated 150,000 light-years across, has a mass of about 2.9–4.8 × 109 solar masses, and rotates at 217 km/s.
It was discovered by Fritz Zwicky in 1941. Zwicky considered his discovery to be "one of the most complicated structures awaiting its explanation on the basis of stellar dynamics."
An estimation of the galaxy's span resulted in a conclusion of 150,000 light years, which is slightly larger than the Milky Way.
Evolution
The galaxy was once a normal spiral galaxy before it apparently underwent a head-on collision with a smaller companion approximately 200 million years ago (i.e., 200 million years prior to the image) When the nearby galaxy passed through the Cartwheel Galaxy, the force of the collision caused a powerful shock wave through the galaxy, like a rock being tossed into a sandbed. Moving at high speed, the shock wave swept up gas and dust, creating a starburst around the galaxy's center portion that were unscathed. This explains the bluish ring around the center, brighter portion.[9] It can be seen that the galaxy is beginning to retake the form of a normal spiral galaxy, with arms spreading out from a central core.
Alternatively, a model based on the gravitational Jeans instability of both axisymmetric (radial) and nonaxisymmetric (spiral) small-amplitude gravity perturbations allows an association between growing clumps of matter and the gravitationally unstable axisymmetric and nonaxisymmetric waves which take on the appearance of a ring and spokes.
X-ray sources
The unusual shape of the Cartwheel Galaxy may be due to a collision with a smaller galaxy such as those in the lower left of the image. The most recent star burst (star formation due to compression waves) has lit up the Cartwheel rim, which has a diameter larger than the Milky Way. Star formation via starburst galaxies, such as the Cartwheel Galaxy, results in the formation of large and extremely luminous stars. When massive stars explode as supernovas, they leave behind neutron stars and black holes. Some of these neutron stars and black holes have nearby companion stars, and become powerful sources of X-rays as they pull matter off their companions. The brightest X-ray sources are likely black holes with companion stars, and appear as the white dots that lie along the rim of the X-ray image. The Cartwheel contains an exceptionally large number of these black hole binary X-ray sources, because many massive stars formed in the rim.
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