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The Hubble Telescope uses the Moon as a mirror to study the Earth



On January 20-21, 2019, planet Earth lies between the Sun and the Moon, covering the rocky mass with its shadow during a total lunar eclipse.

The moon may have faded for us here on Earth, but it serves as a giant moon mirror from space.

NASA’s Hubble Space Telescope used the Moon to reflect sunlight to observe Earth’s atmosphere, detecting the fingerprints of the planet’s ozone layer. By examining Earth’s ozone layer, scientists will be able to detect life-sustaining conditions in worlds other than our own.

Hubble’s observations have been detailed in a study published this week in Journal of Astronomy.

This chart illustrates a total lunar eclipse, showing sunlight being reflected off the Moon.M. Kornmesser (ESA / Hubble), NASA and ESA

Hubble was launched in 1990 and the space telescope has been orbiting low Earth since then.

To observe Earth’s atmosphere, the telescope does not look directly at the planet, but uses the Moon to reflect sunlight that has passed through Earth’s atmosphere during a total lunar eclipse. This chimp is clustered between the Moon and the Sun.

Astronomers have used this method before, but this is the first time that a total eclipse has been captured at ultraviolet wavelengths, between visible light and X-rays, from a space telescope. .

That way, the space telescope could detect the ozone’s spectral fingerprints. Ozone is a gas made up of three oxygen atoms in the Earth’s upper atmosphere, and used as a protective shield from the Sun’s ultraviolet radiation.

Ozone occurs naturally when oxygen in Earth’s atmosphere is exposed to high concentrations of ultraviolet light, acting as a blanket around our planet.

“Photosynthesis is possibly the most efficient metabolic process that can develop on any planet, because it is powered by starlight and uses elements as abundant in the universe as water. and carbon dioxide, “Giada Arney, scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-author of the new study, said in a statement. “These essential ingredients should be common on habitable planets.”

When scientists look for signs of life on other planets, ozone acts as a strong sign of the possibility of life in other worlds.

“The discovery of ozone matters because it’s the product,” said Allison Youngblood, a research fellow at the Laboratory for Atmospheric and Space Physics in Boulder, Colorado and the lead author of the new study. photochemical side effects of molecular oxygen, and itself a byproduct of life. said in a statement.

However, finding oxygen alone is not a sign of life on another planet, there are many other factors to consider before astronomers can confirm a person’s viability. alien planet.

As exoplanets move in front of their host stars, the telescope detects signs of chemicals in the planets’ atmospheres as they filter out certain colors in their light. star. However, smaller planets similar to Earth have thinner atmospheres, which makes detecting this type much more difficult.

Therefore, larger telescopes will be needed to observe the smaller planets.

Hubble’s recent observations of Earth are part of ongoing experiments aimed at perfecting these types of observations as our planet is the only small rocky world we know of as being inhabited by life. . Earth serves as the only perfect and unique analogue for life on other planets.

Abstract: We observed the January 2019 total lunar eclipse using the Hubble Space Telescope STIS spectrometer to obtain the first near ultraviolet (1700–3200 Å) observation of Earth as a Forward alien planets. Observatories and instruments that can perform extraterrestrial transmissions are beginning to be planned, and the determination of the Earth’s transmission spectrum characterization is important to ensure that spectral characteristics. key (eg ozone or O3) appropriately captured in mission concept studies. O3 is produced photochemical from O2A product of metabolism is dominant on Earth today, and it will be sought in future observations as important evidence for life on alien planets. Ground-based observations of lunar eclipses have provided Earth-passing spectra at optical wavelengths and near IR, but O is the strongest3 the signature is in near ultraviolet. We describe the observations and methods used to extract transmission spectra from Hubble eclipse spectra and determine the spectral characteristics of O3 and Rayleigh scattering in the 3000–5500 Å region in the Earth’s transmission spectrum by comparison with Earth models including the effect of refraction in the atmosphere on the ground during a lunar eclipse. Our near-ultraviolet spectrum is unremarkable, the consequence of missing out on a narrow period in a lunar eclipse when sunlight near ultraviolet light is not completely degraded through Earth’s atmosphere. because O is very strong3 absorption and when sunlight is transmitted to the lunar surface at the height where it passes through O3 layer rather than above it.


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