From today’s first press conference at the AAS meeting, astronomers have found that two of the fundamental objects they use as units of measure might not be as reliable a unit of measure as they thought.
- Astronomers have discovered that the Cepheid variable stars that they use to estimate the distances to the nearest galaxies are not necessarily the stars they thought. At least two Cepheids, which are variable stars, do not pulse reliably (one actually stopped pulsing entirely). Another is surrounded by a previously unknown nebula cloud, which affects its apparent brightness, an essential data-point when using these stars as a measuring tool. Here’s one press release.
- The Crab Nebula threw out some gigantic gamma ray bursts last fall. In addition, astronomers have found that the nebula actually flickers wildly, and is also changing in gamma ray energy output over the long term, declining by seven percent in the last two years. No one yet knows what exactly causes these different variations. Like Cepheids, the Crab has been used as a standard for measuring the energy of astronomical gamma ray objects. This is no longer reliable. Here’s one press release, plus images.