The International Space Station. Credit: NASA
Monday, June 24, 2013
Sunday, June 23, 2013
PLANET FAR FROM ITS STAR
FROM: NASA
NASA'S Hubble Uncovers Evidence of Farthest Planet Forming From Its Star
WASHINGTON -- Astronomers using NASA's Hubble Space Telescope have found compelling evidence of a planet forming 7.5 billion miles away from its star, a finding that may challenge current theories about planet formation.
Of the almost 900 planets outside our solar system that have been confirmed to date, this is the first to be found at such a great distance from its star. The suspected planet is orbiting the diminutive red dwarf TW Hydrae, a popular astronomy target located 176 light-years away from Earth in the constellation Hydra the Sea Serpent.
Hubble's keen vision detected a mysterious gap in a vast protoplanetary disk of gas and dust swirling around TW Hydrae. The gap is 1.9 billion miles wide and the disk is 41 billion miles wide. The gap's presence likely was caused by a growing, unseen planet that is gravitationally sweeping up material and carving out a lane in the disk, like a snow plow.
The planet is estimated to be relatively small, at 6 to 28 times more massive than Earth. Its wide orbit means it is moving slowly around its host star. If the suspected planet were orbiting in our solar system, it would be roughly twice Pluto's distance from the sun.
Planets are thought to form over tens of millions of years. The buildup is slow, but persistent as a budding planet picks up dust, rocks, and gas from the protoplanetary disk. A planet 7.5 billion miles from its star should take more than 200 times longer to form than Jupiter did at its distance from the sun because of its much slower orbital speed and the deficiency of material in the disk. Jupiter is 500 million miles from the sun and it formed in about 10 million years.
TW Hydrae is only 8 million years old, making it an unlikely star to host a planet, according to this theory. There has not been enough time for a planet to grow through the slow accumulation of smaller debris. Complicating the story further is that TW Hydrae is only 55 percent as massive as our sun.
"It's so intriguing to see a system like this," said John Debes of the Space Telescope Science Institute in Baltimore, Md. Debes leads a research team that identified the gap. "This is the lowest-mass star for which we've observed a gap so far out."
An alternative planet-formation theory suggests that a piece of the disk becomes gravitationally unstable and collapses on itself. In this scenario, a planet could form more quickly, in just a few thousand years.
"If we can actually confirm that there's a planet there, we can connect its characteristics to measurements of the gap properties," Debes said. "That might add to planet formation theories as to how you can actually form a planet very far out."
The TW Hydrae disk also lacks large dust grains in its outer regions. Observations from the Atacama Large Millimeter Array in Chile show dust grains roughly the size of a grain of sand are not present beyond about 5.5 billion miles from the star, just short of the gap.
"Typically, you need pebbles before you can have a planet. So, if there is a planet and there is no dust larger than a grain of sand farther out, that would be a huge challenge to traditional planet formation models," Debes said.
The team used Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) to observe the star in near-infrared light. The researchers then compared the NICMOS images with archival Hubble data and optical and spectroscopic observations from Hubble's Space Telescope Imaging Spectrograph (STIS). Debes said researchers see the gap at all wavelengths, which indicates it is a structural feature and not an illusion caused by the instruments or scattered light.
The team's paper will appear online June 14 in The Astrophysical Journal.
NASA'S Hubble Uncovers Evidence of Farthest Planet Forming From Its Star
WASHINGTON -- Astronomers using NASA's Hubble Space Telescope have found compelling evidence of a planet forming 7.5 billion miles away from its star, a finding that may challenge current theories about planet formation.
Of the almost 900 planets outside our solar system that have been confirmed to date, this is the first to be found at such a great distance from its star. The suspected planet is orbiting the diminutive red dwarf TW Hydrae, a popular astronomy target located 176 light-years away from Earth in the constellation Hydra the Sea Serpent.
Hubble's keen vision detected a mysterious gap in a vast protoplanetary disk of gas and dust swirling around TW Hydrae. The gap is 1.9 billion miles wide and the disk is 41 billion miles wide. The gap's presence likely was caused by a growing, unseen planet that is gravitationally sweeping up material and carving out a lane in the disk, like a snow plow.
The planet is estimated to be relatively small, at 6 to 28 times more massive than Earth. Its wide orbit means it is moving slowly around its host star. If the suspected planet were orbiting in our solar system, it would be roughly twice Pluto's distance from the sun.
Planets are thought to form over tens of millions of years. The buildup is slow, but persistent as a budding planet picks up dust, rocks, and gas from the protoplanetary disk. A planet 7.5 billion miles from its star should take more than 200 times longer to form than Jupiter did at its distance from the sun because of its much slower orbital speed and the deficiency of material in the disk. Jupiter is 500 million miles from the sun and it formed in about 10 million years.
TW Hydrae is only 8 million years old, making it an unlikely star to host a planet, according to this theory. There has not been enough time for a planet to grow through the slow accumulation of smaller debris. Complicating the story further is that TW Hydrae is only 55 percent as massive as our sun.
"It's so intriguing to see a system like this," said John Debes of the Space Telescope Science Institute in Baltimore, Md. Debes leads a research team that identified the gap. "This is the lowest-mass star for which we've observed a gap so far out."
An alternative planet-formation theory suggests that a piece of the disk becomes gravitationally unstable and collapses on itself. In this scenario, a planet could form more quickly, in just a few thousand years.
"If we can actually confirm that there's a planet there, we can connect its characteristics to measurements of the gap properties," Debes said. "That might add to planet formation theories as to how you can actually form a planet very far out."
The TW Hydrae disk also lacks large dust grains in its outer regions. Observations from the Atacama Large Millimeter Array in Chile show dust grains roughly the size of a grain of sand are not present beyond about 5.5 billion miles from the star, just short of the gap.
"Typically, you need pebbles before you can have a planet. So, if there is a planet and there is no dust larger than a grain of sand farther out, that would be a huge challenge to traditional planet formation models," Debes said.
The team used Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) to observe the star in near-infrared light. The researchers then compared the NICMOS images with archival Hubble data and optical and spectroscopic observations from Hubble's Space Telescope Imaging Spectrograph (STIS). Debes said researchers see the gap at all wavelengths, which indicates it is a structural feature and not an illusion caused by the instruments or scattered light.
The team's paper will appear online June 14 in The Astrophysical Journal.
Saturday, June 22, 2013
STRANGE MARS
FROM: NASA
We were looking at these strange features on Mars. They're what we call, "linear gullies," because they're long troughs. They can extend up to two kilometers, which is just over a mile and they're really strange because they go down and then they end abruptly in a pit.
A lot of features on the Earth that are similar do end in a debris apron because stuff has been moved from the top to the bottom. But these don't have the apron. They just have a pit at the end. And so we were wondering how they could form.
Frozen carbon dioxide accumulates on the surface and we think that some of this accumulation will compress down and actually form ice slabs and ice blocks.
We bought some frozen carbon dioxide dry ice blocks and we took it out to a dune slope, and we put it down and we saw what happened.
Most dune slopes will be at 33 degrees and that's a nice steep slope. And so we did it with a water ice block and the sand got wet and it didn't move. And we did it with a wooden block and, you know, it moved three inches and then it stopped.
The dry ice block, we expected it to see a bit more activity, but we didn't expect it to just move and move and move and move and keep moving all the way to the bottom. But even on the other side of the dune, which is more like six degrees -- it's very shallow -- we put the block on and we pushed it and it would just slide right down and the only reason it stopped was because it hit the bushes at the bottom.
Dry ice, as it heats up, turns into gas that pushes against the sand as it comes out. After a few hours, it's scooped out a nice little area. And so you have a feature that looks like what we see on Mars. They will move down that dune slope and carve out a shallow trough.
When the block of ice is on the sand surface, that sand is just a little bit warmer. And so it causes a cushion of air to form. And that lifts that block just a little bit so when it moves forward, it's like its lubricated and it can just slide very easily.
And when it got to the bottom, instead of just sitting there, it would disappear as the area heated up and then that could possibly leave a pit.
I'm looking forward to the day when astronauts can engage in a whole new area of extreme sports. They could snowboard down these carbon dioxide covered dunes on a cushion of carbon dioxide. They would just shoot right down those slopes. It would be amazing.
We were looking at these strange features on Mars. They're what we call, "linear gullies," because they're long troughs. They can extend up to two kilometers, which is just over a mile and they're really strange because they go down and then they end abruptly in a pit.
A lot of features on the Earth that are similar do end in a debris apron because stuff has been moved from the top to the bottom. But these don't have the apron. They just have a pit at the end. And so we were wondering how they could form.
Frozen carbon dioxide accumulates on the surface and we think that some of this accumulation will compress down and actually form ice slabs and ice blocks.
We bought some frozen carbon dioxide dry ice blocks and we took it out to a dune slope, and we put it down and we saw what happened.
Most dune slopes will be at 33 degrees and that's a nice steep slope. And so we did it with a water ice block and the sand got wet and it didn't move. And we did it with a wooden block and, you know, it moved three inches and then it stopped.
The dry ice block, we expected it to see a bit more activity, but we didn't expect it to just move and move and move and move and keep moving all the way to the bottom. But even on the other side of the dune, which is more like six degrees -- it's very shallow -- we put the block on and we pushed it and it would just slide right down and the only reason it stopped was because it hit the bushes at the bottom.
Dry ice, as it heats up, turns into gas that pushes against the sand as it comes out. After a few hours, it's scooped out a nice little area. And so you have a feature that looks like what we see on Mars. They will move down that dune slope and carve out a shallow trough.
When the block of ice is on the sand surface, that sand is just a little bit warmer. And so it causes a cushion of air to form. And that lifts that block just a little bit so when it moves forward, it's like its lubricated and it can just slide very easily.
And when it got to the bottom, instead of just sitting there, it would disappear as the area heated up and then that could possibly leave a pit.
I'm looking forward to the day when astronauts can engage in a whole new area of extreme sports. They could snowboard down these carbon dioxide covered dunes on a cushion of carbon dioxide. They would just shoot right down those slopes. It would be amazing.
Friday, June 21, 2013
Wednesday, June 19, 2013
Tuesday, June 18, 2013
Monday, June 17, 2013
Sunday, June 16, 2013
THE BUTTERFLY IN THE SCORPION
FROM: NASA The Butterfly Nebula
The bright clusters and nebulae of planet Earth's night sky are often named for flowers or insects. Though its wingspan covers over 3 light-years, NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the dying central star of this particular planetary nebula has become exceptionally hot, shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust.
This sharp and colorful close-up of the dying star's nebula was recorded in 2009 by the Hubble Space Telescope's Wide Field Camera 3, installed during the final shuttle servicing mission. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is near the center of this view, almost edge-on to the line-of-sight. Molecular hydrogen has been detected in the hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius). Image Credit: NASA/ESA/Hubble
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