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Tag Archives: Keck

Adapted from a UCLA press release, November 3, 2014.

For years, astronomers have been puzzled by a bizarre object in the center of the Milky Way that was believed to be a hydrogen gas cloud headed toward our galaxy’s enormous black hole. (See Section 15.5, Chapter opener figure, p. 382, and Figure 15-5, p. 388.)

Having studied it during its closest approach to the black hole this summer, UCLA astronomers believe that they have solved the riddle of the object widely known as G2.

A team led by Andrea Ghez determined that G2 is most likely a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust – its movements choreographed by the black hole’s powerful gravitational field. The research is published today in the journal Astrophysical Journal Letters.

Astronomers had figured that if G2 had been a hydrogen cloud, it could have been torn apart by the black hole, and that the resulting celestial fireworks would have dramatically changed the state of the black hole. However, G2 survived and continues on its orbit unaffected.

G2 appears to be just one of an emerging class of stars near the black hole that are created because the black hole’s powerful gravity drives binary stars to merge into one. In our galaxy, massive stars primarily come in pairs. The star suffered an abrasion to its outer layer but otherwise will be fine.

Keck Observatory

Credit and copyright: Ethan Tweedie Photography

The team utilized the Keck Observatory’s adaptive optics technology, a powerful technology that corrects the distorting effects of the Earth’s atmosphere in real time to more clearly reveal the space around the supermassive black hole.

Links: full UCLA press release, Keck press release.


Astronomers have discovered a distant quasar illuminating a vast nebula of diffuse gas, revealing for the first time part of the network of filaments thought to connect galaxies in a cosmic ‘web’. Researchers at the University of California, Santa Cruz, led the study, published January 19 in the journal, Nature. Using the 10-meter Keck I telescope in Hawaii, the researchers detected a very large, luminous nebula of gas extending about 2 million light-years across intergalactic space.


Credit: S. Cantalupo (UCSC); Joel Primack (UCSC); Anatoly Klypin (NMSU)

The standard cosmological model of structure formation in the Universe predicts that galaxies are embedded in a cosmic web of matter, most of which (about 84 percent) is invisible dark matter. This web is seen in the results from computer simulations of the evolution of structure in the Universe, which show the distribution of dark matter on large scales, including the dark matter halos in which galaxies form and the cosmic web of filaments that connect them. Gravity causes ordinary matter to follow the distribution of dark matter, so filaments of diffuse, ionized gas are expected to trace a pattern similar to that seen in dark matter simulations.

Until now, these filaments have never been seen. Intergalactic gas has been detected by its absorption of light from bright background sources, but those results don’t reveal how the gas is distributed. In this study, the researchers detected the fluorescent glow of hydrogen gas resulting from its illumination by intense radiation from the quasar.

The hydrogen gas illuminated by the quasar emits ultraviolet light known as Lyman alpha radiation. The distance to the quasar is so great (about 10 billion light-years) that the emitted light is “stretched” by the expansion of the Universe from an invisible ultraviolet wavelength to a visible shade of violet by the time it reaches the Keck telescope and the spectrometer used for this discovery. Knowing the distance to the quasar, the researchers calculated the wavelength for Lyman alpha radiation from that distance and built a special filter to get an image at that wavelength.

Links: further images and information via the full Keck Observatory press release.