Red dwarfs are the most abundant type of stars in our galaxy. They are smaller and cooler than our Sun, but they are presumed to contain the bulk of the galaxy’s planet population, perhaps tens of billions of worlds. Surveys by the Kepler Space Telescope and other observatories have shown that rocky planets are common around these stars, and there are several such planets within the habitable zones of nearby red dwarfs. The temperate climates on such worlds could allow for oceans of water to exist on their surfaces, creating environments suitable for life. However, many of these rocky planets may not harbor water and organic material, the necessary ingredients for life as we know it. Earth formed as a “dry” planet and was later bombarded over hundreds of millions of years with icy material from comets and asteroids from the outer Solar System. If that’s the processes needed for planets to become possible habitats for life around, then planets around red dwarfs may be in trouble.
Observations of the nearby, young red dwarf AU Microscopii (AU Mic) using the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope in Chile shows a rapidly eroding dust-and-gas disk encircling the star. Hubble took the image above in 2018 in visible light. The glare of the star, located at the center of the disk, has been blocked out. The box in the picture highlights one blob of material extending above and below the disk.
The disk is being cleaned out by fast-moving blobs of material which pushing small objects out of the system. (Astronomers aren’t sure what’s driving the process, but one theory is that powerful mass ejections from the star, a common phenomenon among young red dwarfs, may bee the cause.) If the debris disk around AU Mic continues to dissipate at the current pace, it wont last much more than 1.5 million years, the blink of an eye in cosmic time. Planets would be too large to be ejected, but smaller bodies, such as comets and asteroids, could be cleared out. Then with no later bombardment by watery bodies, the planets might end up dry, dusty, and lifeless.
Image Credits: NASA / ESA / J. Wisniewski (University of Oklahoma) / C. Grady (Eureka Scientific) / G. Schneider (Steward Observatory)
This animation flies through the local galactic neighborhood to the Triangulum galaxy (M33), a smaller spiral than our Milky Way galaxy. It first zooms in on one of M33’s bright regions of star birth, the nebula cataloged as NGC 604, a glowing cloud of hot ionized hydrogen gas..
Video Credit: NASA / ESA / STScI
This animation shows the coldest brown dwarf found to date. It also the fourth closest system to our Sun. WISE J085510.83-071442.5 is a very dim object that was noticed because of its rapid motion across the sky. It first showed up in two infrared images taken six months apart in 2010 by the Wide-field Infrared Survey Explorer, or WISE (the orange triangles). Two more images of the object were taken with the Spitzer Space Telescope in 2013 and 2014 (green triangles). Because the two satellites are in different orbits, their data could be used to calculate the distance to the brown dwarf: 7.2 light-years. The Spitzer data were used to show that the body appears to be roughly the same temperature as the Earth’s North Pole (-48 to -13 °C).
Image Credit: NASA
This video clip covers about 36 hours of Solar activity as seen by the Solar Dynamics Observatory in January, 2014. A large active region sported tall coils of magnetic field lines that stretched many times the size of Earth above the Sun. When viewed in extreme ultraviolet light, the field lines are revealed as particles move along them. Some lines connect with another active region that has rotated out of view. This close-up also shows darker, cooler plasma just above the surface being tugged back and forth by magnetic forces.
Video Credit: NASA
Brian May is not only a musician. He’s also an astrophysicist who is part of the New Horizons science team.
Video Credit: Brian May / Queen
Red/Green glasses required.
Image Credit: NASA
This is a view of Saturn partially lit in crescent phase, a view that can only be seen when the object is between the observer and the Sun. From the Earth, we can only see Mercury and Venus in varying crescent phases and Mars and the other outer planets fully lit. Because the Moon can be either between the Earth and the Sun or farther away, we see it go through all the phases from New to Full to New again.
This picture of Saturn was made by the Cassini spacecraft.
As the data download from New Horizons proceeds, we should soon have pictures from an similar point of view of the Kuiper Belt Object Ultima Thule.
Image Credit: NASA