Diamonds in the Sky
There’s a lot of beauty and violence in the universe and recent astronomy news seems to highlight both aspects of our galactic home.
Two studies in Nature this week examine the awakening of a distant galaxy's dormant black hole as it shredded and consumed a star. Confirmed by both NASA’s Swift satellite and ground-based radio telescopes, the Draco galaxy is so far away, it took the light from the event approximately 3.9 billion years to reach Earth.
The black hole in Draco resides at the center of a far-off galaxy and is about the same size as the 4-million-solar-mass black hole marking the Milky Way’s heart. Although our galaxy's black hole is currently quiet, this discovery means just one wayward star can spark a spectacle.
More consumption… according to several online news outlets, white dwarfs are swallowing up rocky planets, similar to (gulp) Earth. Science News reports:
Remains of rocky bodies that once circled the white dwarfs pepper the gas envelopes around the dead stars. The ratios of elements in these remains — called “pollution,” since it mars the star’s normally pristine hydrogen or helium atmosphere — tell astronomers what the bodies were made of and where they might have come from. Although about as common as normal stars in the Milky Way, white dwarfs aren’t the most obvious choice for astronomers looking for traces of extrasolar planets — but, it turns out, the dense, collapsed stars may be incredibly useful.
And how do you turn a white dwarf into a spectacular planet? According to Australian researchers, just add a pulsar. The team thinks that the object is all that remains of a once-massive white dwarf, most of whose matter was siphoned off towards the pulsar. What was once the core of the star is now a planet, made entirely of diamond!
The discovery is an exciting addition to the known pulsar-planet systems. But this is the first observation reporting a planet that formed so directly from a star.
And from diamonds to cold stars—as cold as the human body?! Of course we’re talking about brown dwarfs, and when talking about brown dwarfs, of course we’re discussing data from NASA's Wide-field Infrared Survey Explorer (WISE). This week, astronomers working with WISE data have discovered the coldest class of star-like bodies.
Called Y dwarfs, these stars are nearly impossible to see when viewed with a visible-light telescope. WISE's infrared vision allowed the telescope to spot the faint glow of six Y dwarfs relatively close to our sun, within a distance of about 40 light-years.
The Y's are the coldest members of the brown dwarf family. Brown dwarfs are sometimes referred to as “failed” stars. They are too low in mass to fuse atoms at their cores and thus don't burn with the fires that keep stars like our sun shining steadily for billions of years. Instead, these objects cool and fade with time, until what little light they do emit is at infrared wavelengths.
“Finding brown dwarfs near our sun is like discovering there's a hidden house on your block that you didn't know about,” NASA JPL’s Michael Cushing says. “It's thrilling to me to know we've got neighbors out there yet to be discovered. With WISE, we may even find a brown dwarf closer to us than our closest known star.”
And finally, speaking of dwarfs… In case you didn’t know, this week marked the five-year anniversary of Pluto’s demotion to a dwarf planet. If you are still mourning the loss, be sure to read “Pluto-killer” Mike Brown’s recent blog post, “Free the dwarf planets.”
Image: Aurore Simonnet/Sonoma State University