If you’re in love with space then you’ll fall head over heels for this: it’s a picture of Earth taken from the Voyager 1 spacecraft after it passed the orbit of Pluto back in 1990—on Valentine’s Day, no less. That image of our planet from almost 4 billion miles away inspired Carl Sagan to write his famous “Pale Blue Dot” passage, which reminds us that we are all just riding on “a mote of dust suspended in a sunbeam.”
Voyager 2 may have been the second of NASA’s famous twin exploration spacecraft but it launched first, on August 20, 1977. Eight and a half years later it became the first (and last) spacecraft to visit Uranus, at 31,500 miles across the third largest planet in the Solar System. Voyager 2 made its closest pass by Uranus 31 years ago, giving us our best views to this day of the enormous ice giant and its moons.
At first glance this pixelated picture may not look all that spectacular, but it gains a whole new meaning when you realize what it’s actually showing: a look at the most distant crescent moon ever seen! But this isn’t Earth’s moon; it’s Charon, Pluto’s largest companion, lit by the light from a Sun 3.2 billion miles away—some of it even reflected off Pluto.
Observations from some of the world’s most powerful telescopes—NASA’s Chandra X-ray Observatory, the Giant Metrewave Radio Telescope (GMRT) in India, the National Science Foundation’s Karl G. Jansky Very Large Array in New Mexico, and Japan’s Subaru Telescope in Hawai’i have been combined to create an image of two incredibly powerful cosmic forces colliding, two billion light-years away. Hot gas fired out from supermassive black holes inside one cluster of galaxies is accelerated to high speeds when it meets the shockwaves caused by a collision with a neighboring cluster, huge interactions spanning hundreds of thousands of light-years but only visible in X-ray and radio wavelengths.
The dwarf planet Ceres, at 587 miles wide the largest object in the main asteroid belt between Mars and Jupiter, has a different surface composition than previously thought—and it took NASA and DLR’s Boeing 747-based SOFIA observatory to make the distinction. By observing Ceres in mid-infrared, only possible from high altitudes above infrared-absorbing water vapor, SOFIA found that Ceres is covered in silicates—pyroxenes—that likely came from impacts, the result of infalling material from elsewhere in the asteroid belt…the “dust” of asteroid collisions.
Like anything else, stars have life spans. They are born (from collapsing clouds of interstellar dust), they go through a long main phase where they fuse various elements in their cores, and eventually they die when they run out of fuel. The finer details of these steps are based on what the star is made of, how massive it is, and what sort of company it keeps. Stars like our Sun have lifespans in the 9-10 billion year range—of which ours is near the middle—but other stars can have much shorter or longer lifespans, and as astronomers look out into the galaxy they can find stars at all different phases of their lives…of course, the longer a phase lasts, the more likely it is to find stars existing within it. We’ve found stars that are only a few thousand years old and we know of regions where stars are, right now, in the process of being born, but what is the oldest star we know of?
Actually, it’s not all that far away, in cosmic terms. Just 190 light-years distant in our own galaxy, HD 140283 (aka the Methuselah star) is, as of 2013, the oldest star ever discovered. Based on its stage as a subgiant and its remarkably low amount of heavy elements, astronomers have estimated the age of this star as 14.3 billion years old. Now this number is actually more than the estimated age of the Universe itself, but don’t worry—there’s a reason for that.
Read the rest of this story by astronomer Phil Plait on Slate here: The Oldest Known Star in the Universe.