Astronomers have begun searching for exoplanets – planets orbiting stars at distances where liquid water could exist – that may host life, similar to Earth. Many come from stars that offer suitable temperatures without being too hot or too cold and could support life on these new worlds.
They are widely considered the top candidates for searching extraterrestrial life.
Mars
Discovery of primitive extraterrestrial life would generate headlines and set records for clicks, but the real prize lies in finding a thriving alien civilization. Astronomers must look towards the stars for any evidence of technology transmitted via radio waves that might indicate alien presence.
After years of false starts in finding habitable planets in our Milky Way galaxy, our chances have greatly improved thanks to numerous discoveries made since. Kepler space telescope’s work reveals that at least 20% of nearby stars host planets within their habitable zone – the range where liquid water can remain on planet surfaces.
Astronomical discoveries have also provided a boost for exobiology, the search for extraterrestrial life. NASA’s Cassini satellite revealed geysers erupting from Enceladus’ ice surface, suggesting it may hold an ocean filled with salty liquid water; and New Horizons probe discovered evidence suggesting Pluto may possess its own ocean as well.
Telescopic observations indicate that Mars once contained lakes and oceans. Furthermore, radar has revealed evidence of liquid water likely residing a few kilometers below its surface – perhaps as much as several kilometers deep underground! We have even discovered evidence that hardy microorganisms such as Deinococcus radiourans might thrive there as on Earth.
The Sun
Astronomers initially focused on searching for Earth-size planets orbiting stars with similar temperatures and brightness levels as our own; but today the search encompasses far wider potential worlds. Over the last five decades, we have found thousands of exoplanets that orbit their parent stars at exactly the right distance for liquid water to exist on rocky surfaces, while over a dozen star systems exist within several light years from where conditions could support life.
The Sun’s core can produce enough heat to boil a glass of water in less than six seconds, yet its surface, known as the photosphere, only reaches 10,000 degrees Fahrenheit (5,500 degC). As we move outward from its core region, temperatures gradually decline until they reach around 3.5 million F (2 million degC) in its convection zone region where large bubbles of plasma (a mix of charged atoms) swirl about.
As stars progress along their “main sequence” of evolution, they will inevitably run out of hydrogen fuel and expand into red giants – eventually swallowing Mercury, Venus and any terrestrial planets along their path. Turnbull established her criteria on several factors, such as age and metallicicity. Stars that are too young may display flares and other forms of activity while those more massive than our sun often don’t live long enough to support life on Earth. Star spectra provide us with insights into their elemental composition; when sunlight strikes a star’s surface, its atoms absorb certain wavelengths that create dark lines on its spectrum; this gives scientists information on which elements compose its makeup (such as oxygen, carbon or nitrogen in relation to hydrogen).
The Moon
The Moon is our best chance of discovering alien life within the Solar System, as its ice-covered surface might conceal geological activity beneath. Some rocks even exhibit residual magnetism indicating previous magnetic activity on its surface. Furthermore, evidence of subsurface oceans have been detected, potentially due to gravitational pull between Neptune and Moon.
Astronomers have given exobiology an incredible boost with the discovery of thousands of Earth-sized planets orbiting other stars, providing prime candidates for life as they orbit at distances that could support liquid water – essential for life on our planet. Furthermore, many of the stars hosting these planets are “Goldilocks” stars – not too hot nor cold and with brightness levels suitable for future telescopes to directly image their planets.
NASA’s defunct Kepler telescope identified TOI-700’s rocky planets as potentially home for life; TESS will explore them further. Another potentially promising target could be TRAPPIST-1 – a red dwarf 40 light years away that hosts seven terrestrial-sized planets within its habitable zone – though their discovery remains unverified at present.
The Stars
Stars form the fundamental building blocks of galaxies. Stars emerge when gravity compresses clouds of gas and dust into dense masses that heat up sufficiently, compressing enough for hydrogen fusion that produces light as well as other electromagnetic radiation.
Astronomers have discovered thousands of planets orbiting other stars. Most are Earth-sized and orbit their parent stars at distances which allow liquid water to exist on the surface – which makes them excellent candidates for hosting extraterrestrial life. Many were first discovered by NASA’s now defunct Kepler space telescope, while many more are being explored with TESS mission.
One of TESS’s candidates, TOI-700, is a red dwarf which shares similarities with our Sun but is much denser and thus less active and stable; therefore it should not strip its orbiting planets of their atmospheres so quickly; additionally it means that planets around TOI-700 may withstand its harsh radiation for extended periods.
Betelgeuse in Orion will one day explode into a spectacular fireball visible by humans. Rigel, the seventh brightest star in the night sky and known by Bedouin people of Negev and Sinai during the 7th Century CE as Suhayl, provided another landmark used by explorers as they navigated their way in darkness.
