NASA – In biology, “symbiosis” refers to two organisms that live close to and interact with one another. Astronomers have long studied a class of stars – called symbiotic stars – that co-exist in a similar way. Using data from NASA’s Chandra X-ray Observatory and other telescopes, astronomers are gaining a better understanding of how volatile this close stellar relationship can be.
R Aquarii (R Aqr, for short) is one of the best known of the symbiotic stars. Located at a distance of about 710 light years from Earth, its changes in brightness were first noticed with the naked eye almost a thousand years ago. Since then, astronomers have studied this object and determined that R Aqr is not one star, but two: a small, dense white dwarf and a cool red, giant star.
The red giant star has its own interesting properties. In billions of years, our Sun will turn into a red giant once it exhausts the hydrogen nuclear fuel in its core and begins to expand and cool. Most red giants are placid and calm, but some pulsate with periods between 80 and 1,000 days like the star Mira and undergo large changes in brightness. This subset of red giants is called “Mira variables.”
The red giant in R Aqr is a Mira variable and undergoes steady changes in brightness by a factor of 250 as it pulsates, unlike its white dwarf companion that does not pulsate. There are other striking differences between the two stars. The white dwarf is about ten thousand times brighter than the red giant. The white dwarf has a surface temperature of some 20,000 K while the Mira variable has a temperature of about 3,000 K. In addition, the white dwarf is slightly less massive than its companion but because it is much more compact, its gravitational field is stronger. The gravitational force of the white dwarf pulls away the sloughing outer layers of the Mira variable toward the white dwarf and onto its surface. Continue reading →
Hubblesite — These six images, taken by the Hubble Space Telescope, reveal a jumble of misshapen-looking galaxies punctuated by exotic patterns such as arcs, streaks, and smeared rings. These unusual features are the stretched shapes of the universe’s brightest infrared galaxies that are boosted by natural cosmic magnifying lenses. Some of the oddball shapes in the images also may have been produced by spectacular collisions between distant, massive galaxies in a sort of cosmic demolition derby.
This so-called gravitational lensing occurs when the intense gravity of a massive galaxy or cluster of galaxies magnifies the light of fainter, more distant background sources. The “lenses” are foreground massive galaxies whose gravity magnifies and distorts images of the distant bright infrared galaxies behind them.
The faraway galaxies are as much as 10,000 times more luminous than our Milky Way. The lensing phenomenon allows for features as small as about 100 light-years or less across to be seen in the background galaxies.
The galaxies existed between 8 billion and 11.5 billion years ago, when the universe was making stars more vigorously than it is today. The galaxies are ablaze with runaway star formation, pumping out more than 10,000 new stars a year. The star-birth frenzy creates lots of dust, which enshrouds the galaxies, making them too faint to detect in visible light. But they glow fiercely in infrared light, shining with the brilliance of 10 trillion to 100 trillion suns.
The infrared galaxies in these images are part of a Hubble survey of 22 distant ultra-luminous infrared galaxies that were found by ground- and space-based observatories. The images were taken in infrared light by Hubble’s Wide Field Camera 3. Color has been added to highlight details in the galaxies.
Here’s a nice perspective on how huge Saturn really is compared to Mimas(upper right).
Image: NASA/JPL-Caltech/Space Science Institute
NASA — The low angle of sunlight along the slim crescent of Saturn’s moon Enceladus (313 miles or 504 kilometers across) highlights the many fractures and furrows on its icy surface.
This view looks toward the Saturn-facing hemisphere of Enceladus, which is dimly illuminated in the image above by sunlight reflected off Saturn. North on Enceladus is up and rotated 14 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Dec. 26, 2016.
The view was obtained at a distance of approximately 104,000 miles (168,000 kilometers) from Enceladus. Image scale is 3,303 feet (1 kilometer) per pixel.
mage credit: NASA/JPL-Caltech/Space Science Institute/Cornell University
NASA/JPL – Working with image data from NASA’s Cassini mission, researchers have found evidence that Saturn’s moon Enceladus may have tipped over, reorienting itself so that terrain closer to its original equator was relocated to the poles. This phenomenon is known as true polar wander.
Researchers discovered a chain of basins across the surface of Enceladus along with a pair of depressions that line up with an equator and poles, respectively, if the moon’s axis of rotation was reoriented by about 55 degrees of latitude.
These maps look toward the icy moon’s southern hemisphere, with colors representing highs and lows. Purple represents the lowest elevations, while red represents the highest.
The map at left shows the surface of Enceladus in its possible ancient orientation, millions of years ago. The chain of basins representing topographic lows can be seen in blue and purple, running along the equator, with an additional low region around the original south pole. The region that encloses the moon’s currently active south polar terrain, with its long, linear “tiger stripe” fractures, would have been at middle latitudes just south of the equator. The map at right shows the current orientation of Enceladus.
The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, California, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.
Rosetta was an epic mission no doubt about it. For some looking at all the data from the mission is the best part; something akin to looking through a treasure chest, you never know what you might find.
In case you missed this landing. Welcome home to Expedition 51 Flight Engineer and Soyuz Commander Oleg Novitskiy of the Russian Federal Space Agency (Roscosmos) and Flight Engineer Thomas Pesquet of ESA (European Space Agency) landed safely near the town of Dzhezkazgan, Kazakhstan.
I must say, I’ve enjoyed following Thomas Presquet during his stay aboard the ISS.
Reminder: The SpaceX launch is scheduled for 21:07 UTC / 17:07 ET and you will find a link for the launch posted about a quarter to the hour.
The weather outlook does not look promising:
From (US) NOAA for Cape Canaveral: Showers likely and possibly a thunderstorm, mainly after noon. Cloudy, with a high near 84. South southwest wind around 5 mph becoming north northeast in the afternoon. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.
So this brings up the question would have the same oxidation processes interfered with life processes at a critical early state or would have it actually assisted them? Good work by Stony Brook and NASA.
NASA — This diagram presents some of the processes and clues related to a long-ago lake on Mars that became stratified, with the shallow water richer in oxidants than deeper water was.
The sedimentary rocks deposited within a lake in Mars’ Gale Crater more than three billion years ago differ from each other in a pattern that matches what is seen in lakes on Earth. As sediment-bearing water flows into a lake, bedding thickness and particle size progressively decrease as sediment is deposited in deeper and deeper water as seen in examples of thick beds (PIA19074) from shallowest water, thin beds (PIA19075) from deeper water and even thinner beds (PIA19828) from deepest water.
At sites on lower Mount Sharp, inside the crater, measurements of chemical and mineral composition by NASA’s Curiosity Mars rover reveal a clear correspondence between the physical characteristics of sedimentary rock from different parts of the lake and how strongly oxidized the sediments were. Rocks with textures indicating that the sediments were deposited near the edge of a lake have more strongly oxidized composition than rocks with textures indicating sedimentation in deep water. For example, the iron mineral hematite is more oxidized than the iron mineral magnetite.
An explanation for why such chemical stratification occurs in a lake is that the water closer to the surface is more exposed to oxidizing effects of oxygen in the atmosphere and ultraviolet light.
On Earth, a stratified lake with a distinct boundary between oxidant-rich shallows and oxidant-poor depths provides a diversity of environments suited to different types of microbes. If Mars has ever hosted microbial live, the stratified lake at Gale Crater may have similarly provided a range of different habitats for life.