Researchers using data from NASA's Kepler space telescope have shown that migrating planets stop their inward journey before reaching their stars, as illustrated in this artist's concept. Jupiter-like planets, called "hot Jupiters" are known to migrate from their star's frigid outer reaches in toward the star and its blistering heat. Dozens of hot Jupiters have been discovered orbiting closely to their stars, whipping around in just days.
Until now, it was not clear whether these massive planets remain in stable orbits close to their stars or keep marching in closer and closer until they are ultimately consumed. The new work not only demonstrates that the planets stop their migration inward, but also shows how. The tidal, or gravitational, forces acting to circularize the orbits of the planets cause them to cease their inbound travels once they have hit the stable orbits.
This graphic depicts HD 189733b, the first exoplanet caught passing in front of its parent star in X-rays. As described in our press release , NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM Newton Observatory have been used to observe a dip in X-ray intensity as HD 189733b transits its parent star.
The main figure is an artist’s impression showing the HD 189733 system, containing a Sun-like star orbited by HD 189733b, an exoplanet about the size of Jupiter. This “hot Jupiter” is over 30 times closer to its star than Earth is to the Sun and goes around the star once every 2.2 days, as determined from previous observations. Also in the illustration is a faint red companion star, which was detected for the first time in X-rays with these observations. This star orbits the main star about once every 3,200 years.
The inset contains the Chandra image of HD 189733. The source in the middle is the main star and the source in the lower right is the faint companion star. The source at the bottom of the image is a background object not contained in the HD 189733 system.
The exoplanet itself cannot be seen in the Chandra image, as the transits involve measuring small decreases in X-ray emission from the main star. The authors estimate that the percentage decrease in X-ray light during the transits is about three times greater than the corresponding decrease in optical light. This tells them that the region blocking X-rays from the star is substantially larger than the region blocking optical light from the star, helping to determine the size of the planet's atmosphere. The extended atmosphere implied by these results is shown by the light blue color around the planet. Recent observations of HD 189733b with the Hubble Space Telescope have confirmed that the lower atmosphere of the planet has a deep blue color, due to the preferential scattering of blue light by silicate particles in its atmosphere.
For about a decade astronomers have known that ultraviolet and X-ray radiation from the main star in HD 189733 are evaporating the atmosphere of its closely orbiting planet over time. The authors of the new study estimate that HD 189733b is losing between 100 million and 600 million kilograms per second. This rate is about 25% to 65% higher than it would be if the planet's atmosphere were not extended.
At a distance of just 63 light years, HD 189733b is the closest hot Jupiter to Earth, which makes it a prime target for astronomers who want to learn more about this type of exoplanet and the atmosphere around it.
Chandra was used to make observations of six transits by HD 189733b and the team also used archival data from XMM-Newton for one transit. These results are available online and will appear in the August 10th issue of The Astrophysical Journal.
The constellation of Virgo (The Virgin) is the largest of the Zodiac constellations, and the second largest overall after Hydra (The Water Snake). Its most appealing feature, however, is the sheer number of galaxies that lie within it. In this picture, among a crowd of face- and edge-on spiral, elliptical, and irregular galaxies, lies NGC 4866, a lenticular galaxy situated about 80 million light-years from Earth.
Lenticular galaxies are somewhere between spirals and ellipticals in terms of shape and properties. From the picture, we can appreciate the bright central bulge of NGC 4866, which contains primarily old stars, but no spiral arms are visible. The galaxy is seen from Earth as almost edge-on, meaning that the disc structure — a feature not present in elliptical galaxies — is clearly visible. Faint dust lanes trace across NGC 4866 in this image, obscuring part of the galaxy’s light.
To the right of the galaxy is a very bright star that appears to lie within NGC 4866’s halo. However, this star actually lies much closer to us; in front of the galaxy, along our line of sight. These kinds of perspective tricks are common when observing, and can initially deceive astronomers as to the true nature and position of objects such as galaxies, stars, and clusters.
This sharp image of NGC 4866 was captured by the Advanced Camera for Surveys, an instrument on the NASA/ESA Hubble Space Telescope.
By now I'm sure everyone has heard of the explosion in the town of West, Texas. Also I'm sure everyone has seen the two cell phone videos that captured the explosion.
What I decided to do was put those videos together into one video. Using the flash from the explosion as a reference point, I was able to sync both videos together giving the viewer a look at the same event from two different angles.
Using an aerial photograph and landmarks in both videos, I was able to determine the location where both videos were shot. See the photo below
What you also see in the photo is that the entire chemical plant was obliterated. The railroad tracks to the left of the plant in the photo were almost fused together by the blast. There was also a playground that was completely destroyed. Just beyond that is the nursing home and apartment that were also completely destroyed.
Below is the video I synced up. On the left is the Father and his daughter. On the right is Erick Perez.
After the explosion the cloud resembled a nuclear mushroom cloud.
Hopefully the town can recover from this disaster. Send your thoughts and prayers.
How far away is "redshift six"? Although humans are inherently familiar with distance and time, what is actually measured for astronomical objects is redshift, a color displacement that depends on exactly how energy density has evolved in our universe. Now since cosmological measurements in recent years have led to a concordance on what energy forms pervade our universe, it is now possible to make a simple table relating observed cosmological redshift, labeled "z", with standard concepts of distance and time, including the extrapolated time since the universe began. One such table is listed above, where redshift z is listed in the first and last columns, while the corresponding universe age in billions of years is listed in the central column. To find the meaning of the rest of the columns, please read the accompanying technical paper. Although stars in our galaxy are effectively at cosmological redshift zero, the most distant supernovae seen occur out past redshift one, which the above chart shows occurred when the universe was approximately half its present age. By contrast, the most distant gamma-ray bursts yet observed occur out past redshift six, occurring when the universe was younger than one billion years old, less than 10 percent of its present age.
