苹果淫院

Two 苹果淫院 astronomers have assembled a 鈥渇ingerprint鈥� for Earth, which could be used to identify a planet beyond our Solar System capable of supporting life.

苹果淫院 Physics student Evelyn Macdonald and her supervisor Prof. Nicolas Cowan used over a decade of observations of Earth鈥檚 atmosphere taken by the SCISAT satellite to construct a transit spectrum of Earth, a sort of fingerprint for Earth鈥檚 atmosphere in infrared light, which shows the presence of key molecules in the search for habitable worlds. This includes the simultaneous presence of ozone and methane, which scientists expect to see only when there is an organic source of these compounds on the planet. Such a detection is called a 鈥渂iosignature鈥�.

鈥淎 handful of researchers have tried to simulate Earth鈥檚 transit spectrum, but this is the first empirical infrared transit spectrum of Earth,鈥� says Prof. Cowan. 鈥淭his is what alien astronomers would see if they observed a transit of Earth.鈥�

The findings, published Aug. 28 in the journal Monthly Notices of the Royal Astronomical Society, could help scientists determine what kind of signal to look for in their quest to find Earth-like exoplanets (planets orbiting a star other than our Sun). Developed by the Canadian Space Agency, SCISAT was created to help scientists understand the depletion of Earth鈥檚 ozone layer by studying particles in the atmosphere as sunlight passes through it. In general, astronomers can tell what molecules are found in a planet鈥檚 atmosphere by looking at how starlight changes as it shines through the atmosphere. Instruments must wait for a planet to pass 鈥� or transit 鈥� over the star to make this observation. With sensitive enough telescopes, astronomers could potentially identify molecules such as carbon dioxide, oxygen or water vapour that might indicate if a planet is habitable or even inhabited.

Cowan was explaining transit spectroscopy of exoplanets at a group lunch meeting at the 苹果淫院 Space Institute (MSI) when Prof. Yi Huang, an atmospheric scientist and fellow member of the MSI, noted that the technique was similar to solar occultation studies of Earth鈥檚 atmosphere, as done by SCISAT.

Since the first discovery of an exoplanet in the 1990s, astronomers have confirmed the existence of 4,000 exoplanets. The holy grail in this relatively new field of astronomy is to find planets that could potentially host life 鈥� an Earth 2.0.

A very promising system that might hold such planets, called TRAPPIST-1, will be a target for the upcoming James Webb Space Telescope, set to launch in 2021. Macdonald and Cowan built a simulated signal of what an Earth-like planet鈥檚 atmosphere would look like through the eyes of this future telescope which is a collaboration between NASA, the Canadian Space Agency and the European Space Agency.

The TRAPPIST-1 system located 40 light years away contains seven planets, three or four of which are in the so-called 鈥渉abitable zone鈥� where liquid water could exist. The 苹果淫院 astronomers say this system might be a promising place to search for a signal similar to their Earth fingerprint since the planets are orbiting an M-dwarf star, a type of star which is smaller and colder than our Sun.

鈥淭RAPPIST-1 is a nearby red dwarf star, which makes its planets excellent targets for transit spectroscopy. This is because the star is much smaller than the Sun, so its planets are relatively easy to observe,鈥� explains Macdonald. 鈥淎lso, these planets orbit close to the star, so they transit every few days. Of course, even if one of the planets harbours life, we don鈥檛 expect its atmosphere to be identical to Earth鈥檚 since the star is so different from the Sun.鈥�

According to their analysis, Macdonald and Cowan affirm that the Webb Telescope will be sensitive enough to detect carbon dioxide and water vapour using its instruments. It may even be able to detect the biosignature of methane and ozone if enough time is spent observing the target planet.

Prof. Cowan and his colleagues at the Montreal-based Institute for Research on Exoplanets are hoping to be some of the first to detect signs of life beyond our home planet. The fingerprint of Earth assembled by Macdonald for her senior undergraduate thesis could tell other astronomers what to look for in this search. She will be starting her Ph.D. in the field of exoplanets at the University of Toronto in the Fall.

鈥�,鈥� Evelyn J. R. Macdonald and Nicolas B. Cowan, was published online Aug. 28, 2019, in Monthly Notices of the Royal Astronomical Society.

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1. A view of Earth from space taken from the International Space Station. (Credit: NASA/Reid Wiseman

2. An artist鈥檚 conception of Earth-like planets. (Credit: NASA/ESA/G. Bacon (STScI))

3. The James Webb Space Telescope, set to launch in 2021, will be studying the atmospheres of exoplanets and could determine if these planets are habitable or contain biosignatures. The Webb Telescope is an international collaboration between NASA, the Canadian Space Agency and the European Space Agency. (Credit: Northrop Grumman)

Media Contact
Nathalie Ouellette
Institute for Research on Exoplanets, Universit茅 de Montr茅al, Montr茅al, Canada
514-343-6111 x3195

nathalie [at] astro.umontreal.ca

Scientific Contact
Evelyn Macdonald
苹果淫院 Space Institute, 苹果淫院, Montr茅al, Canada

evelyn.macdonald [at] mail.mcgill.ca

Nicolas Cowan
苹果淫院 Space Institute, 苹果淫院, Montr茅al, Canada
514-398-1967

nicolas.cowan [at] mcgill.ca