Tommy Johnson

First Detection of Exoplanets With Atmospheres

Alien Life, Astronomy, Astrophysics, Exoplanets, Space Exploration

First Detection of Exoplanets With Atmospheres

Astronomers frequently struggle to detect planets. Their light is extremely dim compared to that of their host star, making it hard for astronomers to observe and measure them accurately.

But with the launch of the James Webb Space Telescope (JWST) this summer, astronomers will be able to study atmospheres with greater detail than ever before. For instance, it can detect molecules such as sulfur dioxide and sodium present in WASP-39b’s atmosphere which orbits an Sun-like star 700 light years away.

1. Transit Spectroscopy

Astronomers have made history by discovering an atmosphere on an exoplanet orbiting another star for the first time ever using transit spectroscopy, an observation technique which observes exoplanet light as it passes in front of its host star and divides reflected light from exoplanets into color bands, like rainbow colors, which provide insight into which molecules make up its atmosphere and where these bands lie within it. Data collected with this method provides valuable information regarding depth, shape and day-night wind patterns – making this method an invaluable source of data collection when studying chemical composition between host star atmosphere and exoplanets orbiting it.

Transit spectroscopy offers an effective alternative to direct imaging by being able to distinguish both large and small planets close to their host stars, including those near Earth. This allows us to search for different atmospheric compositions such as liquid water, silicate hazes and noble gases. Ground-based transit spectroscopy provides more precise measurement of a transiting planet’s mass and radius through measurements of radial velocity and radial velocity measurements, respectively. Ideal targets for ground-based transit spectroscopy are planets with minimum masses under 13MJ such as super-Earths that orbit their parent stars, Neptunes above inhabitable zones of M dwarfs as well as hot Neptunes found near massive M-dwarfs as well as hot Jupiters spotted by transit spectroscopy.

The primary limitation of the spectroscopic approach lies in its inapplicability when planets orbit closer than 180 degrees from their host star. But new telescopes will soon enable us to probe transiting planets as they move along their orbital inclination; this will enable us to identify many more potentially atmosphere-rich objects than has been possible thus far.

Prior to recently, the only reliable way of gathering information about an exoplanet’s atmosphere was through observations in the UV, optical and near-infrared spectrums. Recently however, astronomers have used transit spectroscopy on HD 209458b and HD 189733b gas giant exoplanets to detect helium gas in their atmospheres; furthermore thermal emission observations indicate they both contain haze or clouds.

2. Thermal Emissions

One effective strategy for finding exoplanets is observing them as they pass in front of their host star, known as transits. Telescopes on Earth or in space can detect this dimming effect known as transit, providing scientists with clues to these planets’ atmospheres.

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Astronomers have used techniques like this one to detect gases such as helium and water vapor on some exoplanets, providing more insight into their atmospheric composition than ever before. With James Webb Space Telescope (JWST) we will receive even greater data about these planets’ atmospheres.

The JWST mission may still be several years away from launch, yet its early results are already captivating researchers. For example, its groundbreaking measurements of WASP-39 b’s atmosphere gave researchers definitive proof of carbon dioxide being present on an exoplanet not part of our Solar System; providing important details on their formation while possibly helping predict whether they support life.

Astronomers are currently studying data collected by Kepler and other satellites that have made thousands of discoveries, such as sizes, masses and orbits for each satellite as well as any signs that other gases such as hydrogen, oxygen or carbon monoxide might exist. Astronomers hope that using this information they can refine models of planet atmospheres to better understand how they might have formed over time.

An alternative method for detecting gases in exoplanet atmospheres is through thermal emissions. A telescope can use light refraction measurements to gauge surface temperatures on exoplanets, then determine their atmospheric temperatures by monitoring how much light is reflected or absorbed – hot planets will reflect more light while cold ones absorb more. Astronomers can also search for blue-green tinted emissions caused by cyanobacteria when living in hot acidic environments.

As scientists gain more information about these distant planets, their atmospheres could enable more detailed direct images to be made of exoplanets – providing scientists with a glimpse of their surfaces and possibly even signs of life on them. Unfortunately, direct imaging requires telescopes that remain completely still for hours on end – something currently unattainable through satellites and space-based telescopes.

3. Optical Emissions

Astronomers aim to explore the atmospheres of exoplanets to detect any evidence of life, and to do this they need planets close enough to their host stars for light from said star to penetrate some parts of its atmosphere. That is why NASA’s James Webb Space Telescope (JWST), scheduled for launch in 2018, is so anticipated. With it they hope to detect gases such as water, methane, carbon dioxide and many others using transit spectroscopy – an approach which allows researchers to detect multiple gases simultaneously using transit spectroscopy technology.

This technique works by measuring the brightness of a light source as a planet passes in front of it, and then monitoring how that brightness varies over time as its light passes through an atmosphere on which different molecules absorb different colors of light emitted by stars and constellations. By doing so, this technique reveals information on an entire planet’s chemical makeup by looking for missing colors in starlight spectrum spectrums.

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Astronomers utilize the JWST Near-Infrared Spectrograph (NIRSpec). A team analyzed NIRSpec data on WASP-39b, an enormous gas giant approximately 1.3 times larger than Jupiter orbiting a Sun-like star 700 light years away. Their analysis revealed a clear signal of CO2 in its atmosphere – an unprecedented discovery that gives insight into processes involved with planet formation and evolution.

CO2 detection bodes well for future work to identify biosignatures on smaller planets resembling Earth. As JWST continues its survey and more terrestrial exoplanets are discovered, instruments capable of characterizing their atmospheres in order to search for signs of life will become ever-more essential for studying these cosmic worlds.

Step two in this process involves directly imaging newly discovered exoplanets, which is no easy task as direct imaging telescopes require seeing planets at great distances away from their hosts, with minimal glare from these stars making resolution of planet surfaces challenging. Luckily, astronomers have other techniques at their disposal for detecting distant exoplanets like Spitzer Space Telescope and European Southern Observatory’s Very Large Telescope that are effective at picking out faint signals of distant planets; for instance observing how exoplanets “wobble” around host stars – both have successfully found exoplanets through “wobbling”.

4. Infrared Spectroscopy

IR Spectroscopy detects infrared radiation frequencies that have been absorbed by molecules, producing characteristic spectral lines for each molecule (see diagram below). Light of different wavelengths or frequencies is absorbed at different rates depending on their chemical properties – this allows an astronomer to accurately determine and measure atmospheric composition on exoplanets.

Multiple observation techniques are available for detecting exoplanets with atmospheres. These include transmission spectroscopy, reflected spectroscopy and differential absorption spectroscopy (DAS).

Transmission spectroscopy uses a system of mirrors, gratings and slits to disperse incident light into distinct frequency components (see diagram below), each detected by individual detectors before being digitalized and processed through Fourier transform for creation of an infrared spectrum.

Spectrums refer to all frequencies detected by telescopes. To obtain the spectrum of a planet, this telescope will observe it as it travels past its host star; light curves will help identify it as well as measure temperature and cloud coverage in its atmosphere.

Another method for detecting transiting exoplanets involves measuring variations in star brightness caused by short-period planets’ orbits, or their orbital phases, with their host stars. You can detect these fluctuations by comparing intensity during and before/after eclipse with intensity pre/post eclipse – this measurement also serves to establish eccentricity and mass.

Recently, WASP-39b’s atmospheric studies were successfully undertaken using JWST’s transmission spectroscopy instrument. This observation revealed a spectrum that can be well fitted by one-dimensional models with ten times solar metallicity and moderate cloud opacity; features in its data that may indicate absorption by sodium, potassium and water vapour were detected as well. These observations bode well for Webb to probe various atmospheric compositions on exoplanets such as Earth-sized planets in close orbits around their parent stars.

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