By COLIN M. STEWART
By COLIN M. STEWART
Tribune-Herald staff writer
Astronomers at the W.M. Keck Observatory atop Mauna Kea were set to begin using a new instrument Monday night that promises to speed up the process of discovering some of the universe’s oldest, and most distant, objects.
Dubbed MOSFIRE, the infrared instrument was installed earlier this year by a team working with the UCLA Infrared Lab, said project lead scientist Ian McLean. He added that Alan Stockton of the University of Hawaii at Manoa’s Institute for Astronomy was set to be the first person to use the instrument.
“Distant galaxies are very faint, but they are also numerous over any patch of sky. It can take hours to get the tell-tale spectrum of a single, faint, distant galaxy …” McLean stated in a Monday afternoon email in response to questions. “It would be much more efficient, and scientifically valuable, if many galaxies could be observed at the same time.”
MOSFIRE allows such an approach because astronomers will be able to identify up to 46 galaxies in a given field of view, he said. An instrument known as a “configurable slit unit,” or CSU, would then isolate those 46 objects by placing a small slit over each one.
“Only the light from those 46 slits enters the instrument and 46 spectra are recorded simultaneously. It may still take several hours to get a good spectrum, but now you have studied 46 rather than one galaxy!” he wrote.
Being able to study infrared light is important, he explained, because the expanding nature of the universe stretches the light emitted by distant galaxies until it is virtually invisible. What began as visible light ends up being “well into the infrared when it reaches us,” he said.
“But infrared instruments are tricky,” he said. “Infrared radiation is also called thermal or heat radiation, and it comes from everything, the sky, the telescope, and the instrument itself. To eliminate the nearby heat from the instrument, the entire spectrometer with all its lenses, mirrors, mechanisms and digital camera, must be cooled down to cryogenic temperatures inside a vacuum chamber.”
McLean added that the combination of the instrument’s improved optics and infrared detector, mixed with its ability to observe multiple target objects, “makes MOSFIRE an extremely powerful new tool for the Keck Observatory. MOSFIRE will make the discovery of objects like BX442 more frequent.”
In referencing BX442, McLean was speaking of the recent discovery of the universe’s oldest known spiral galaxy, in which Keck astronomers played an important part using another piece of equipment developed at the UCLA Infrared Lab.
In addition to the galaxy’s age, which was pegged at about 10.7 billion years, BX442 excited astronomers because of its symmetrical, spiral structure — something scientists did not believe could happen at the young age of just 3 billion years after the Big Bang.
“As you go back in time to the early universe … galaxies look really strange, clumpy and irregular, not symmetric,” said UCLA astronomer Alice Shapley in a July release issued by the Keck Observatory. “The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?”
The discovery, which was detailed this summer in the journal “Nature,” could reveal clues as to why galaxy spirals begin to take shape.
Email Colin M. Stewart at cstewart@hawaiitribune-herald.com.