My Science School

The largest planet in our solar system, Jupiter, is located fifth from the Sun. It is more than two times the size of all the planets in our solar system combined. Jupiter has also been instrumental in our understanding of the universe and our place in it. In 1610, Galileo discovered Jupiter's four large moons: lo, Europa, Ganymede and Callisto. This confirmed the Copernican view that the Earth was not the centre of the universe as these newly discovered celestial objects were revolving around another planet.

It is estimated that eleven Earths could fit across Jupiter's equator. To put it in other words, if our planet is the size of a grape, then Jupiter is the size of a basket-ball. It has an iconic Great Red Spot, which is a giant storm that has been active in Jupiter's atmosphere for hundreds of years. This storm is bigger than the Earth!

Jupiter's orbit is about 778 million kilometres or 5.2 Astronomical Units (AU) from the Sun (Earth is one AU from the Sun). Jupiter is a gas giant, which lacks an Earth-like atmosphere. Even if it has a solid inner core at all, it would only be about the size of the Earth. Jupiter's atmosphere contains mainly hydrogen (H) and helium (He) and has more than 75 moons. It rotates about its axis once every 10 hours (a Jovian day), and takes about 12 Earth years to complete one revolution about its orbit around the Sun (a Jovian year).

In the year 1979, NASA's Voyager mission discovered Jupiter's faint ring system. We have discovered that all the four giant planets of our solar system have ring systems. Till date, nine spacecraft have visited Jupiter. Of them, only the most recent one landed on Jupiter. Seven of them only flew by this gas giant and the other two just orbited it. Juno, the latest spacecraft, arrived on Jupiter in 2016.

Although it is the biggest planet in our solar system, Jupiter cannot support life as we know it. But we have come to know that some of its moons have oceans beneath their crusts, which could possibly support some form of life.

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Researchers find out an often overlooked key role played by the orbit of Jupiter on Earth.

Most planets have eccentric orbits. While circular orbits around a star would ensure that the distance between the star and the planet never changes, these eccentric orbits mean that the planets traverse around a star in an oval-shape. As a result, the planet would receive more heat when it goes closer to the star, affecting the planet's climate.

Alternative solar system

Based on this knowledge and using detailed data from the solar system as we know it today, researchers from the University of California Riverside created an alternative solar system. In this hypothetical theoretical system, they were able to show that if Jupiter's orbit were to become more eccentric, then it would lead to big changes in Earth's orbit, thereby making the Earth more hospitable than it is currently.

This is because Jupiter in this theoretical system would push Earth's orbit to be even more eccentric. As a result, parts of Earth would sometimes get closer to the sun. This would mean that even parts of Earth's surface that are now sub-freezing will get warmer. In effect, the habitable range on the surface of the Earth would be increased.

Assumptions proven wrong

 The findings of this research, published in September in Astronomical Journal, go against two long-held scientific beliefs with respect to our solar system. One of these is that the current avatar of Earth is the best in terms of habitability. The second one is that changes to Jupiter's orbit could only be bad for Earth.

Apart from upending these long-held assumptions, the researchers are looking to apply their findings in the search of exoplanets - habitable planets around other stars. While existing telescopes are adept at measuring a planet's orbit, the same cannot be said about measuring a planet's tilt towards or away from a star- another factor that could affect habitability.

The model developed in this research helps us better understand the impact of the biggest planet in our solar system, Jupiter, on Earth's climate through time. Additionally, it also paves the way to find out how the movement of a giant planet is crucial in making predictions about habitability of planets in other systems.

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Discovery about an Earth-like planet orbiting an M dwarf could imply that planets orbiting the most common star may be uninhabitable.

Is Earth the only planet that supports life? This is one of the many questions for which we don't have an answer yet. In a universe filled with countless stars and innumerable planets, our quest for life on a planet other than our own continues.

A new discovery could serve as a signpost and maybe even dramatically narrow our search for life on other planets. The discovery, explained in the Astrophysical Journal Letters in October by researchers from the University of California - Riverside, reveals that an Earth-like planet orbiting an M dwarf appears to have no atmosphere at all.

Most common type of star M dwarfs or red dwarfs are the most common type of star in the universe. This discovery could therefore imply that a large number of planets orbiting these stars may also lack atmospheres, and will therefore likely not support life.

The planet named GJ 1252b is slightly larger than our Earth, but is much closer to its star, an M dwarf, than the Earth is to the sun. On a single day on Earth, this planet orbits its star twice.

In order to find out if this planet lacks an atmosphere, astronomers measured infrared radiation from the planet as its light was during a secondary eclipse. In a secondary eclipse, the planet passes behind the star, and hence the planet's light along with the light reflected from its star are blocked.

Scorching temperatures

The radiation revealed the planet's daytime temperatures to be of the order of 2,242 degrees Fahrenheit. This, along with assumed low surface pressure, led the astronomers to believe that GJ 1252b lacks an atmosphere.

The researchers concluded that the planet will not be able to hold on to an atmosphere, even if it had tremendous amounts of carbon dioxide, which traps heat. Even if an atmosphere builds up initially, it would taper off and erode away eventually.

With M dwarf stars having more flares, the likelihood of planets surrounding them closely holding onto their atmospheres goes down further. The lack of atmosphere means that life as we know it is unlikely to flourish.

In Earth’s  solar neighbourhood, there are about 5,000 stars and most of them are M dwarfs. If planets surrounding them can be ruled -out entirely in the search for life based on this discovery, that would leave roughly around 1,000 stars similar to the sun that could be habitable.

For now, however, these can't be ruled out entirely. Nor can we rule out the possibility of a planet far enough away from an M dwarf star such that it retains its atmosphere. We need more research and results as we continue to embark on our search for life elsewhere.

Picture Credit : Google