At the end of the 19th century, astronomer Simon Newcomb announced that astronomy as a research endeavor had reached an end, that man had approached “…the limit of all we can know about astronomy.” This was in 1889, years before Einstein introduced Relativity, Hubble identified the Andromeda as a separate galaxy, and astronomy changed irrevocably. Newcomb would scarcely recognize modern astronomy with its blazars, magnetars, and extra-solar planets. Here are five of the most astonishing astronomical discoveries of recent decades.
5. Super-Massive Black Holes
A black hole is a space-time singularity; a mass left over from a core-collapse supernova that has reached a density so high that even light cannot escape. In the past 10 years, evidence has mounted for something even stranger — galactic or super-massive black holes. At the core of our very own galaxy sits an object known as Sagittarius A* (“A Star”) that is calculated to weigh in at more than 4 million solar masses. Astronomers know this from observing stars whipping around a massive central source at terrific velocities. Once considered science fiction, super-massive black holes may reside at the cores of most galaxies, and may even have been the seeds that fueled early galaxy growth. And the black hole lurking at the center of our galaxy may be tiny; the black hole at the center of the M87 galaxy is estimated to equal the mass of more than 6.6 billion Suns.
Stars such as our Sun shine by fusing hydrogen into helium. This creates a stability of sorts, with gravity pulling inward while fusion pushes outward. Billions of years from now, as our Sun exhausts its hydrogen fuel, it will expand into a red giant and begin fusing heavier elements. But rare hyper-giant stars larger than 100 solar masses go out in a much more spectacular fashion, erupting as a hypernova and briefly unleashing the energy equivalent of 100 supernovae. Eta Carinae, about 7,500 light years distant is a good candidate for a future hypernova. These are also closely associated with our next cosmic beast on the list …
3. Gamma-Ray Bursts
In the late 1960s, the U.S. launched the Vela series of satellites, aimed at monitoring secret nuclear tests. These soon started detecting gamma-ray flashes from non-terrestrial sources that left astronomers scratching their heads for years. The first hint that the sources of these bursts were extra-galactic came from the fact that they were occurring from random directions in the sky; a nearby source would be biased toward the galactic or solar plane. Throughout the 1990s, the name of the game became pinning down an optical transient and a corresponding red-shift to peg the distance at which these bursts where occurring. Payoff came in 1998 when the BeppoSAX satellite caught an X-ray afterglow from GRB 970228 and placed it at a stupendous distance of over eight billion light years. This makes gamma-ray bursts some of the most energetic events in the known universe. Astrophysical models can account for two types of gamma-ray bursts: long-duration bursts of more than two seconds are thought to be the products of hypernova explosions, and short-period bursts are theorized to be the product of neutron star mergers.
2. A Diamond Exoplanet
It’s amazing to think that prior to 1992, no exoplanets were known. Now planets beyond our solar system are almost weekly news. Among the notable discoveries is a truly bizarre find: WASP-12b. This 1.35 Jupiter-mass world was discovered in 2008 using the SuperWASP planetary transit survey. It whizzes around its host star at a distance of just a little over 2 million miles once every 26 hours, and its cloud tops are a blazing 4,700 degrees Fahrenheit. But the world gets even weirder — recent chemical analysis of the planet’s spectra suggests an abundance of carbon. Surface carbon on this super-sized world may exist as a tarry-sludge, but carbon at depth is more likely to be of the crystalline form we know as diamond. The wealth of “hot-Jupiter” discoveries has shown us that many solar systems are not like our own, although the current methods used to detect these distant solar systems are biased toward discovery of these types of worlds. The prize now is to find a truly Earth-like exoplanet, and the search is also on for the spectral signatures of such chemicals as chlorophyll, which might indicate that life processes have taken hold elsewhere in the universe.