This is the first time that the space telescope has observed such an event
To search for extraterrestrial life, the researchers conducted a dress-up exercise using a world they knew existed: Earth.
As Earth prepares to undergo a lunar eclipse between the Sun and the Moon in January 2019, the Hubble Space Telescope has observed how chemicals in the sky have prevented certain lengths of the sun from reaching the moon. Setting up this observation will mimic how astronomers want to examine the atmosphere of exoplanets like Earth as they pass their stars and filter certain stars.
“We are really pretending to be aliens watching our planet,” said Giada Arney, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
With the help of Hubble, the researchers focused on understanding the effects of atmospheric ozone. Because ozone is both an oxygen chemical produced during photosynthesis and a protective shield that protects life from the sun’s harmful ultraviolet rays, astronomers believe that atmospheric ozone may be a key indicator that a faraway world has a house. During the lunar eclipse, Hubble analyzed sunlight passing through Earth’s atmosphere and reflected off the moon for ozone signatures.
“It is safer for Hubble to see sunlight reflecting off the moon,” said Allison Youngblood, an astronomer at the University of Colorado at Boulder, than to look directly at Earth backlit. Telescope instruments are extremely sensitive and the world is clearly “even on the side of the Hubble Night Frying Detectors”.
These observations revealed significant reductions in some long-range ultraviolet rays absorbed by ozone. Youngblood, Arney, and colleagues report online Aug.6 in the Astronomical Journal.
The data confirmed that chemicals from Earth’s atmosphere filter the expected light, based on the understanding of environmental chemistry researchers. This research gives astronomers more confidence in their ability to identify potentially observable exoplanets.
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