Two sounding rockets are launched from Australia this month, with experiments designed to measure whether the ultraviolet light coming from the stars in the Alpha Centauri system could be harmful to possible life on planets orbiting them. The research will also teach us about how normal – or not – the sun is.
Alpha Centaurionly 4.3 light-years away, consists of two main stars, Alpha Centauri A and Alpha Centauri B (which form a binary pair), and a third star, Proxima Centauri. Although no planets have been positively identified orbiting either Alpha Centauri A or B, if any, ultraviolet light from their stars can have a big impact on whether they host life.
Just the right amount of ultraviolet light can break up simple organic molecules, such as methane, which causes the molecular fragments to be reformed as more complex molecules that are necessary for life. On the other hand, too much ultraviolet light can remove water vapor, allowing it to be removed from a planet’s atmosphere by solar wind and leave the planet dry and barren, as well March is today.
“Understanding ultraviolet radiation is extremely important for understanding what makes a planet habitable“, said Brian Fleming, an astrophysicist at the University of Colorado, Boulder, in a statement (opens in new tab). Fleming is the main investigator for one of the assignments, Dual-channel Extreme Ultraviolet Continuum Experiment (DEUCE). The second experiment launched on a probe rocket is called the Suborbital Imaging Spectrograph for the Transition region Irradiance from Nearby Exoplanet host stars (SISTINE). Probe rockets fly on a parabolic orbit and spend perhaps 20 minutes in space before re-entering the atmosphere, which means that each experiment only has a short time to make observations.
SISTINA was launched first, on Wednesday (July 6), from Arnhem Space Center in Australia’s Northern Territory. It was the second launch ever from the privately owned commercial space center after June launch of NASA’s X-ray quantum calorimeter. If all goes well, DEUCE will be blown up on July 12. Each mission will travel a suborbital orbit on NASA’s two-stage Black Brant IX sound rocket.
The missions must start from the southern hemisphere because the Alpha Centauri system is not visible above a latitude of 29 degrees north, and just around the horizon from Florida, while it is high in the sky as seen from Australia. SISTINE collects data at longer long-ultraviolet wavelengths while DEUCE complements it by looking at shorter extreme-ultraviolet wavelengths, with some overlap between the two experiments so that data can be calibrated and used as a data set.
Observing stars in ultraviolet light is difficult, because ozone layer in Earth’s atmosphere blocks ultraviolet light, forcing scientists to send ultraviolet telescopes into space. At the same time, the interstellar medium of gas and dust between the stars also absorbs ultraviolet light, so all stars that are a considerable distance away can not be observed very clearly in ultraviolet light.
As such, we have complete ultraviolet observations for only one star, the Solar. But how typical are the sun’s ultraviolet emissions? Astronomers do not know; they need ultraviolet readings from other stars to find out. Alpha Centauri A and B are good targets for study, for two reasons. First, they are close, so their ultraviolet light is not attenuated by the interstellar medium. Second, they have masses and temperatures similar to the sun.
“Looking at Alpha Centauri will help us check if other stars like the Sun have the same radiant environment or if there are a variety of environments,” said Kevin France, an astrophysicist at the University of Colorado, Boulder and lead researcher at SISTINE. in the statement.
The three rocket launches from the Arnhem Space Center are the first launches by NASA from a commercial spaceport outside the United States. (NASA has launched from Australia before – most recently in 1995 – but those rockets were detonated from the Royal Australian Air Force Woomera Range Complex.)
“This commercial launch range in Australia opens up new access to the southern hemisphere’s night sky, expanding the possibilities for future science missions,” said Thomas Zurbuchen, Deputy Administrator of NASA’s Science Mission Directorate. statement (opens in new tab).
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