Ultraviolet rocketeers: Cosmic hydrogen fuel

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  • Published: Jan 7, 2016
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
thumbnail image: Ultraviolet rocketeers: Cosmic hydrogen fuel

Sensitive mission

The Great Barred Spiral Galaxy in the constellation Fornax is, at 200,000 light-years across, one of the largest galaxies known to astronomers. IMAGE: ESO, IDA, DANISH 1.5 M, R. GENDLER, J-E. OVALDSEN, C. THÖNE, AND C. FERON

US rocketeers launched the most sensitive instrument they’ve ever used to explore space, recording ultraviolet observations of hydrogen gas, the main fuel of star formation that pervades all galaxies.

Astrophysicist Stephan McCandliss of Johns Hopkins University, Bethesda, Maryland, USA and colleagues have launched their instrument aboard an unmanned rocket that lifted off from the White Sands Missile Range in New Mexico. The rocket ascended to an altitude of more than 270 kilometres and took a snapshot of the Great Barred Spiral Galaxy 56 million light-years away with the rocket's onboard spectrographic telescope built by the McCandliss team recorded ultraviolet light observations of hydrogen gas surrounding the galaxy. The rocket took a parabolic flight lasting a mere 15 minutes from liftoff to parachute deployment but this gave the telescope plenty of time to record data well above the UV filtering effects of the Earth’s atmosphere. The instrument is dubbed FORTIS, for “Far ultraviolet Off-Rowland circle Telescope for Imaging and Spectroscopy.

The flight was part of NASA’s Sounding Rocket Program, which supports about twenty scientific missions a year, exploring space at relatively low cost. With the support of NASA, McCandliss and his team worked for about six years up to early 2013 building the $3.2 million telescope. FORTIS also can simultaneously target and record many spectra from several targets automatically. Moreover, its array of light-reflecting mirrors reduces the number of “bounces” so that photonic loss is minimized. This is actually the third FORTIS mission, previously it targeted another galaxy far, far away and the much closer Comet Ison, but those missions were hampered by technical problems. The current mission seems to have gone as planned and promises to reveal much useful data.

We got data

“We got data; we got spectra,” McCandliss says, adding that there was still a lot of information to be downloaded from the instrument. He said a couple of grids used to filter out charged particles were lost, but that did not appear to have compromised the information collected. The data gathered by FORTIS revolves around light from bright spots in the spiral arms of the target galaxy, which are being fed by gas flowing in from the surrounding circumgalactic medium. Those spots are the regions showing significant gas ebb and flow, which astronomers consider to be the requisite activity that feeds star formation.

The stars are coming out

The team concedes that it will take months to analyse all the data but ultimately it will add up to a greater understanding of how galaxies sustain themselves and what makes them stop producing new stars. The team’s hypothesis is that ultraviolet radiation from new stars temporarily stifles star formation, regulating the rate at which stars form.

McCandliss hopes that the success of the microshutter array in a far ultraviolet application will qualify its use in orbital missions, such as a newly conceived ultraviolet/optical High Definition Space Telescope (HDST), proposed last summer by an international consortium, the Association of Universities for Research in Astronomy. The HDST will outshine the Hubble Space Telescope in terms of image quality and resolution and might even allow astronomers to get an almost close-up view of earth-like planets elsewhere in our galaxy and beyond.

Related Links

Profile, 2016, online: "Stephan McCandliss"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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