My Science School

The moon Io is the most volcanically active world in the solar system. Io even has lakes of molten silicate lava on its surface.

However, Io is a very tiny moon that is enormously influenced by the gravity of the giant planet Jupiter. The gravitational attraction of Jupiter and its other moons exert such strong "pulls" on Io that it deforms continuously from strong internal tides. These tides produce a tremendous amount of internal friction. This friction heats the moon and enables the intense volcanic activity.

Io has hundreds of visible volcanic vents, some of which blast jets of frozen vapor and "volcanic snow" hundreds of miles high into its atmosphere. These gases could be the sole product of these eruptions, or there could be some associated silicate rock or molten sulfur present. The areas around these vents show evidence that they have been "resurfaced" with a flat layer of new material. These resurfaced areas are the dominant surface feature of Io. The very small number of impact craters on these surfaces, compared to other bodies in the solar system, is evidence of Io's continuous volcanic activity and resurfacing.

Credit : Geology.com

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Jupiter is the largest planet in the solar system. Jupiter is so big that all the other planets in the solar system could fit inside it. More than 1,300 Earths would fit inside Jupiter.

Naturally, Jupiter has the strongest magnetic field of all the planets, with a field that is 20,000 times that of Earth’s magnetic field. The gravity is much different too. Having more gravitational pull, someone standing on Jupiter would measure 2.4 times their Earth weight on Jupiter. That means if you weigh 120 pounds on Earth, then you would weigh 288 pounds on Jupiter.

Earth is much smaller than Jupiter. Earth is about 3,959 miles, while Jupiter measures in at 43,441 miles. Earth is 5.972 × 10^24 kg, while Jupiter is 1.898 × 10^27 kg. While Earth only has one moon, Jupiter has 16 confirmed moons. Jupiter also has four rings.

With such a size different, it only makes sense that 1,300 Earths could fit inside of Jupiter. It would take 3.5 Earths alone just to fit across Jupiter’s red spot. Jupiter is massive compared to our tiny planet, so it would naturally take this many Earths to fill Jupiter.

Credit : The Nine Planets

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A year on Mercury takes 87.97 Earth days; it takes 87.97 Earth days for Mercury to orbit the sun once.

Mercury's highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the Sun. It speeds around the Sun every 88 days, traveling through space at nearly 29 miles (47 kilometers) per second, faster than any other planet.

Mercury spins slowly on its axis and completes one rotation every 59 Earth days. But when Mercury is moving fastest in its elliptical orbit around the Sun (and it is closest to the Sun), each rotation is not accompanied by sunrise and sunset like it is on most other planets. The morning Sun appears to rise briefly, set, and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset for other parts of the surface. One Mercury solar day (one full day-night cycle) equals 176 Earth days – just over two years on Mercury.

Mercury's axis of rotation is tilted just 2 degrees with respect to the plane of its orbit around the Sun. That means it spins nearly perfectly upright and so does not experience seasons as many other planets do.

Credit : NASA Science

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Most neutron stars are observed as pulsars. Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. Pulsars have very strong magnetic fields which funnel jets of particles out along the two magnetic poles. 

The Crab pulsar is rather young (only about 960 years old) and has a short period, whereas other, older pulsars have already slowed to longer periods. Pulsars thousands of years old have lost too much energy to emit appreciably in the visible and X-ray wavelengths, and they are observed only as radio pulsars; their periods are a second or longer.

There is one other reason we can see only a fraction of the pulsars in the Galaxy. Consider our lighthouse model again. On Earth, all ships approach on the same plane—the surface of the ocean—so the lighthouse can be built to sweep its beam over that surface. But in space, objects can be anywhere in three dimensions. As a given pulsar’s beam sweeps over a circle in space, there is absolutely no guarantee that this circle will include the direction of Earth. In fact, if you think about it, many more circles in space will not include Earth than will include it. Thus, we estimate that we are unable to observe a large number of neutron stars because their pulsar beams miss us entirely.

Credit : Lumena

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A supernova is the biggest explosion that humans have ever seen. Each blast is the extremely bright, super-powerful explosion of a star.

One type of supernova is caused by the “last hurrah” of a dying massive star. This happens when a star at least five times the mass of our sun goes out with a fantastic bang!

All that energy exploding out does a few things. It scatters the fundamental building blocks of the universe that form the core of most stars: hydrogen, helium, carbon. The resulting cloud of debris forms a nebula, which we talked about recently.

Thus, a supernova is a part of the circle of celestial life. Simba would be proud.

But, that compression from the collapse of a star also causes the core to become super dense. The resulting star core is called a white dwarf. Typically the size of Earth, a white dwarf has the same mass as a star in a much smaller package, making it incredibly dense. It does not give off light thanks to fusion, like most stars. Instead, it gives off thermal radiation that can be visible to scientists.

If the star is big enough, this super dense core can become a black hole.

Credit : Space Centre

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A low or medium mass star (with mass less than about 8 times the mass of our Sun) will become a white dwarf. A typical white dwarf is about as massive as the Sun, yet only slightly bigger than the Earth.

Smaller stars, however, will take a slightly more sedate path. Low- to medium-mass stars, such as the sun, will eventually swell up into red giants. After that, the stars shed their outer layers into a ring known as a planetary nebula (early observers thought the nebulas resembled planets such as Neptune and Uranus). The core that is left behind will be a white dwarf, a husk of a star in which no hydrogen fusion occurs.

Smaller stars, such as red dwarfs, don't make it to the red giant state. They simply burn through all of their hydrogen, ending the process as a dim white dwarf. However, red dwarfs take trillions of years to consume their fuel, far longer than the 13.8-billion-year-old age of the universe, so no red dwarfs have yet become white dwarfs.

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The Kepler space telescope was a space telescope launched by NASA to discover Earth-size planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched on March 7, 2009, into an Earth-trailing heliocentric orbit. 

In 2013, Kepler was assigned a new mission called "K2." Two of the spacecraft's reaction wheels had failed, so engineers came up with a clever scheme to redesign the mission. K2 still hunted for planets, but it scanned a larger swath of sky than before, along the ecliptic plane. The mission began new types of research as well, such as the study of objects within our solar system, exploded stars, and distant supermassive black holes at the hearts of galaxies.

After nine years in deep space collecting data that indicate our sky to be filled with billions of hidden planets - more planets even than stars - NASA's Kepler space telescope has run out of fuel needed for further science operations. NASA has decided to retire the spacecraft within its current, safe orbit, away from Earth. Kepler leaves a legacy of more than 2,600 planet discoveries from outside our solar system, many of which could be promising places for life.

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Gamma Cephei Ab is an exoplanet approximately 45 light-years away in the constellation of Cepheus (the King). The planet was confirmed to be in orbit around Gamma Cephei A in 2002, but was first suspected to exist around 1988 (making this planet arguably the first true exoplanet discovered).

On September 24, 2002, Gamma Cephei Ab was finally confirmed. The team of astronomers (including William D. Cochran, Artie P. Hatzes, et al.) at the Planetary Systems and their Formation Workshop announced the preliminary confirmation of a long-suspected planet Gamma Cephei Ab with a minimum mass of 1.59 MJ (1.59 times that of Jupiter). The parameters were later recalculated when direct detection of the secondary star Gamma Cephei B allowed astronomers to better constrain the properties of the system. Gamma Cephei Ab moves in an elliptical orbit with a semimajor axis of 2.044 AU which takes almost two and a half years to complete. The eccentricity is 0.115, which means it moves between 1.81 and 2.28 AUs in orbital distance around Gamma Cephei A, which would place it from slightly beyond the orbit of Mars, to the inner Asteroid belt in the solar system.

Hipparcos data taken in 2006 constrains its mass below "13.3 MJ at the 95% confidence level, and 16.9 MJ at the 99.73% (3 ?) confidence level". This is not much to go on, but it is enough to verify that it is not another unseen brown or red dwarf.

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An exoplanet is any planet beyond our solar system. Most orbit other stars, but free-floating exoplanets, called rogue planets, orbit the galactic center and are untethered to any star.

Planets are much fainter than the stars they orbit. Hence, exoplanets are extremely difficult to detect. By far, the most successful technique for finding and studying exoplanets has been the radial velocity method, which measures the motion of host stars in response to gravitational tugs by their planets. Swiss astronomers Michel Mayor and Didier Queloz discovered the first planet using this technique, 51 Pegasi b, in the 1990s. Other techniques that have detected exoplanets are - pulsation timing, microlensing, and direct imaging.

The nearest exoplanets are located 4.2 light-years from Earth and orbit Proxima Centauri, the closest star to the Sun.

 In 2011 the Kepler said that they had discovered a planet, Kepler-22b, that was the first to be found in the habitable zone of a star like the Sun. They also discovered the first Earth-sized exoplanets, Kepler-20e and Kepler-20f. By the end of its mission in 2018, Kepler had discovered 2,741 planets, about two-thirds of all known exoplanets.

Credit : Business Standard

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