Transits of Venus (top) and Mercury (bottom) across the edge of the Sun. A year in Mercury is 88 days, yet a Mercury day is 176 Earth days. Mercury is the closest planet to the sun. So not only does Mercury receive four times as … Venus makes the hottest planet in the solar system, after which it is Mercury. If any planet in our Solar System were going to be the hottest, you would have to think it would be Mercury.. Nice. If we’re being quantitative, it’s actually extremely hot! If Mercury were double its size or Venus were half of its size, neither one would have its temperature change by any appreciable amount. Mercury is nearly tidally locked to the Sun – also known as a gravitational lock – and over time this has slowed the rotation of the planet to almost match its orbit around the Sun. Because although Mercury is the closest planet to the sun, it does not have an atmosphere. The blanket-like effect of the clouds and atmospheric gases lift our planet’s climate into the temperate zone where life-as-we-know it has thrived for so long. The fact that Venus is nearly twice as far from the Sun, however, matters a great deal. Although Mercury is the closest to the sun, it’s not the hottest planet. The hottest planet is Venus (at 462 Celsius)" 1- It’s not that Mercury isn’t hot. Comparing these two worlds, there are four very stark differences: As far as absorbing and radiating heat goes, it turns out that size doesn’t matter very much. Comparing these two worlds, there are four very stark differences: As far as absorbing and radiating heat goes, it turns out that size doesn’t matter very much. Venus is the hottest planet in the Solar System because it is close to the Sun and it … System. While Earth isn’t at risk of the same fate, Venus stands as both the hottest world in our Solar System and a cautionary tale of an out-of-control greenhouse effect. This strange occurrence did more than just puzzle astronomers when they first discovered it; it mortified them! Image credit: Wikimedia Commons user WP, under a c.c.-by-s.a.... [+] 3.0 license. The Moon’s average albedo is only about 0.12, which means only 12% of the light that hits it get reflected, while the other 88% gets absorbed. Can We Outrun Dark Energy In The Race To See The Universe? Why Mercury isn’t the Solar System’s hottest planet. The link between the Sun, the atmosphere and the planet’s fate is written all over each world in our Solar System. Images credit: NASA / SDO / HMI / Stanford Univ., Jesper Schou (top); NASA's TRACE Satellite (bottom). Image credit: NASA-APL. Sick. Venus is the hottest planet in our solar system with an average temperature of … It’s up to humanity to learn those lessons and decide what we do next. The Moon’s average albedo is only about 0.12, which means only 12% of the light that hits it get reflected, while the other 88% gets absorbed. The very cold, polar regions of the Earth have a mean temperature far below the rest of the planet:... [+] approximately -20 Celsius. The blanket-like effect of the clouds and atmospheric gases lift our planet's climate into the temperate zone where life-as-we-know it has thrived for so long. I have won numerous awards for science writing. But if a planet’s various orbital parameters were the only things that determined temperature, then the closest planet to the Sun would inevitably be the hottest, and they would all get progressively cooler as we moved farther and farther away. Image credit: Wikimedia Commons user Jonathan Chone, under a c.c.a.-s.a.-4.0 international license, modified by E. Siegel. A day on Mercury lasts 59 Earth days. Smallest. Its density is due to the fact that it is composed of metals and rock. And yet, when you measure the temperature of Venus, there's a surprise: Venus is the same temperature at all times, day or night, at an average of 735 Kelvin (462 °C / 863 °F), making it even hotter than Mercury! An object with an albedo (Bond Albedo, for the geophysicists) of 0 is a perfect absorber, while an object with an albedo of 1 is a perfect reflector. © 2020 Forbes Media LLC. With a diameter of 12,014 kilometers (7,465 miles), Venus is only slightly smaller than our planet. Despite its proximity to our star, Mercury is not the hottest planet in the solar system. Time on Mercury. ... Why is Venus the hottest planet in the solar system? If it weren’t for Earth’s atmosphere, the mean temperature on our planet would be a paltry 255 Kelvin (-18 °C / -1 °F), or approximately the temperature of the Antarctic continent. The lower an object’s albedo is, the better it is at absorbing light, which means the higher the albedo, the less sunlight actually gets absorbed. Has liquid water and shit. Image credit: Toby Smith of the University of Washington’s Astronomy Department. (Without an external heat source, most planetary temperatures would equilibrate at -270 °C / -455 °F.) That’s the story of the closest planet to the Sun: Mercury. The lower an object’s albedo is, the better it is at absorbing light, which means the higher the albedo, the less sunlight actually gets absorbed. mercury also has a long night (several months, due to a complicated orbital resonance that causes mercury to have 3 days every two times it orbits the sun), allowing the heated surface to cool down. Images credit: NASA / SDO / HMI / Stanford Univ., Jesper Schou (top); NASA's TRACE Satellite (bottom). However, even though Mercury is the closest planet to the Sun, it is actually cooler than Venus. While radioactivity and gravitational contraction might supply a substantial amount of energy to the cores of massive planets, the light and heat emitted from our parent star is overwhelmingly responsible for a planet’s surface temperature. From an average distance of 36 million miles (58 million kilometers), Mercury is 0.4 astronomical units away from the Sun. This makes Mercury closer to the Sun than the others. This is why temperatures heat up during the day and cool off during the night, something that’s pretty much true for every planet that has both a day side and a night side. But in the right amounts, atmospheric heat-trapping can be the best thing ever to happen to a world. Closest planet to the sun and still not as spicy as Venus? Yet if you saw two close-up pictures of the recent transits of Mercury (last month) and Venus (in 2012), you’d notice that the Sun appears to “curve” around Venus, while there’s no such effect on Mercury. As the light from the Sun spreads out through space, a more distant world intercepts less and less of its energy. This is also called retrograde rotation. This difference is completely irrelevant. Mercury is one of the five bright planets in our solar system … As the light from the Sun spreads out through space, a more distant world intercepts less and less of its energy. This strange occurrence did more than just puzzle astronomers when they first discovered it; it mortified them! This difference is completely irrelevant. It likely had the same potential for life and biological processes, but a runaway catastrophe created the permanent inferno that’s inhabited our sister world for billions of years. During the day, the planets absorb energy from the Sun, but during both the day and the night, they radiate energy back into space. Mercury is visible to the naked eye. If Mercury were double its size or Venus were half of its size, neither one would have its temperature change by any appreciable amount. (Without an external heat source, most planetary temperatures would equilibrate at -270 °C / -455 °F.) Image credit: Wikipedia’s page on Bond Albedo, with data from R Nave at Ga. State and NASA. We can check this expectation by starting at the innermost planet and working our way outwards. The brightness distance relationship, and how the flux from a light falls off as one over the... [+] distance squared. There are 2 main reasons why Mercury is not the hottest planet within our solar system despite it being much closer to the Sun than Venus ever is within its orbital cycle. Note the overall white appearance in both... [+] cases. You may opt-out by. That’s just embarrassing. Mercury is an airless world, not unlike the Moon. Its atmosphere has excessive amounts of greenhouse gases that warm the planet. It likely had the same potential for life and biological processes, but a runaway catastrophe created the permanent inferno that's inhabited our sister world for billions of years. Its also believed to have a central iron core and a rocky mantle (much … That low temperature is incredibly cold, and far colder than any known naturally occurring temperatures here on Earth. Venus is the second planet from the sun and has a temperature that is maintained at 462 degrees Celsius, no matter where you go on the planet. Mercury is hot. Mercury is the only terrestrial planet that still has hydrogen and helium in its atmosphere. Mercury is the most cratered planet. How reflective or absorptive an object happens to be is known as its albedo, which comes from the latin word albus, meaning white. In the grand scheme of the Solar System, the greatest source of energy by far is the Sun. Most people find this to be an amazing fact, but the reason for this is actually quite easy to explain. Mercury's atmosphere does not contain CO2 (because of which all the heat is returned to space). Mercury is the smallest planet in our solar system—only slightly larger than Earth's Moon. With a radius of 1,516 miles (2,440 kilometers), Mercury is a little more than 1/3 the width of Earth. The Hottest Planet. Even though Mercury is the nearest planet to the Sun, it is not the hottest. Because although Mercury is the closest planet to the sun, it does not have an atmosphere. A year on Mercury lasts 88 Earth days. This sulfuric acid haze, which extends for more than 20 km in thickness, encircles the planet at speeds from 210 to 370 km/hr, trapping the vast majority of the radiated heat and transferring it all across the planet. Mercury is not the hottest planet in the solar system even though it is so close to the sun because Venus has a very thick atmosphere full of carbon dioxide which traps heat but mercury doesn't even have an atmosphere. Mercury is the smallest and innermost planet in the Solar System.Its orbit around the Sun takes 87.97 Earth days, the shortest of all the planets in the Solar System. Not only does Venus possess an atmosphere many times the thickness of Earth’s, loaded with huge amounts of infrared-absorbing gases like carbon dioxide, but it’s shrouded in terrifically thick layers of highly reflective clouds. If you were standing on the equator of Mercury at noon, the temperature rises to 700 kelvin (427° C or 800° F). We can check this expectation by starting at the innermost planet and working our way outwards. Why isn’t Mercury the Hottest Planet? Venus? For airless Mercury, all of that heat goes immediately back into space. Every other planet has something cool about them except this loser. This was an observation that cried out for an explanation, and so we began contrasting the two innermost planets. Atmosphere of Venus. Don’t let the Moon's white appearance fool you! Venus wasn’t large enough to generate its own heat, and yet it was hotter at Venusian midnight than at Mercurian high noon. You see, Mercury and Venus don’t just absorb light from the Sun; each planet then re-radiates that energy as heat back into space. While Earth isn't at risk of the same fate, Venus stands as both the hottest world in our Solar System and a cautionary tale of an out-of-control greenhouse effect. However, mercury is not the hottest planet in the solar system. The Universe is out there, waiting for you to discover it. It’s plenty hot. I am a Ph.D. astrophysicist, author, and science communicator, who professes physics and astronomy at various colleges. The eight planets of the Solar System. Yet early in the Solar System's history, with a cooler Sun and a much thinner atmosphere, Venus was probably similar in temperature to Earth's today. Each quantum of infrared radiation — the re-radiated heat — has got to get through that thick, thick atmosphere, which is difficult. The Moon, for example, looks to have a pretty high albedo to our eyes, with a white appearance during both the day and night. Planets absorb sunlight based on their cross-sectional surface area -- proportional to their radius squared -- and radiate it away in the exact same proportion. Global mosaic of the planet Mercury by NASA's Messenger spacecraft. The moon at night and during the day, as seen from Earth. We also expect seasons — cool times and warm times — based on both how elliptical a planet’s orbit is and on its axial tilt. This sulfuric acid haze, which extends for more than 20 km in thickness, encircles the planet at speeds from 210 to 370 km/hr, trapping the vast majority of the radiated heat and transferring it all across the planet. Mercury has no atmosphere, while Venus has a very thick atmosphere. Any object that’s twice as far away from the Sun receives only one quarter the amount of solar energy per-unit-area, meaning Mercury should receives about four times as much energy on every part of its surface as Venus does. Radiation from the Sun is absorbed by the planet, and the infrared heat emitted is trapped by the carbon dioxide, which creates a runaway greenhouse effect. It is the closest to the sun, and its name is synonymous with temperature because of the metal of the same name which used to be in thermometers. Each quantum of infrared radiation -- the re-radiated heat -- has got to get through that thick, thick atmosphere, which is difficult. Relative sizes and distances (to scale, but not simultaneously) of the inner planets of the Solar... [+] System. You see, Mercury and Venus don’t just absorb light from the Sun; each planet then re-radiates that energy as heat back into space. It's not as close to the Sun as Mercury, but its thick atmosphere,mostly made up of carbon dioxide and its runaway greenhouse effect, make it extremely hot. Mercury is a terrestrial planet. So what makes Venus hotter than Mercury? Perhaps a gas giant that was large enough to generate a significant fraction of its own heat would change that order (if Jupiter and Neptune were swapped, this might be the case), but in general we'd expect a planet's temperature to drop in proportion to its distance from the Sun. Mercury is hot. While radioactivity and gravitational contraction might supply a substantial amount of energy to the cores of massive planets, the light and heat emitted from our parent star is overwhelmingly responsible for a planet's surface temperature. Note how Venus' atmosphere... [+] diffracts sunlight around it, while Mercury's lack of atmosphere shows no such effects. Image credit: ESA/IPEV/PNRA–B. But in the right amounts, atmospheric heat-trapping can be the best thing ever to happen to a world. And yet, Venus is still hotter, which tells us that something else important must be going on with one of the other two points. read less Because it’s so close to the sun, you might think Mercury would also be the hottest planet, but that’s actually not the case. This is the great advantage of Mercury, which encounters nearly four times the flux per square meter compared to Venus. It does not have any natural satellites or rings, and it rotates from east to west, i.e., in the opposite direction to most other planets. All Rights Reserved, This is a BETA experience. This is why temperatures heat up during the day and cool off during the night, something that’s pretty much true for every planet that has both a day side and a night side. The reason why Mercury is not the hottest planet is that it is very dense. Mercury has a very weak atmosphere so it can’t hold any heat. Yet early in the Solar System’s history, with a cooler Sun and a much thinner atmosphere, Venus was probably similar in temperature to Earth’s today. distance squared. Mars? Image credit: Wikimedia Commons user Jonathan Chone, under a c.c.a.-s.a.-4.0 international license, modified by E. Siegel. As the closest planet to the Sun, it completes an orbit in just 88 Earth-days, achieving a maximum temperature during the day of a whopping 700 Kelvin (427 °C / 800 °F) at its hottest, equatorial locations. Image credit: NASA. “There is no question that climate change is happening; the only arguable point is what part humans are playing in it.” –David Attenborough. mercury is much closer to the sun, so it receives more heat. In reality, all physical objects have an albedo between 0 and 1. 10 Surprising Places In Space With The Right Raw Ingredients For Life, Dark Matter’s Biggest Problem Might Simply Be A Numerical Error, Five Surprising Truths About Black Holes From LIGO, UGC 2885, the Rotation Curves of Galaxies, and Dark Matter. Image credit: NASA/ESA. approximately -20 Celsius. Because it is the planet closest to the Sun, it would be easy to think it is also the hottest planet, but that is incorrect. How reflective or absorptive an object happens to be is known as its albedo, which comes from the latin word albus, meaning white. Ultraviolet image of Venus' clouds as seen by the Pioneer Venus Orbiter. Healey, via http://www.esa.int/spaceinimages/Images/2015/03/White_space. Really cool colour and notable for being the hottest planet. Asked by: Akil Answer Mercury is closest to the sun, this is true. Mercury rotates very slowly, so its night side spends a consecutively long time in the dark, shielded from the Sun; during those times, it gets down to just 100 Kelvin (−173 °C / −280 °F). but mercury has no atmosphere, so all of that heat radiates back out to space. Don’t let the Moon’s white appearance fool you! It has extreme temperatures- both cold and ho… And yet, when you measure the temperature of Venus, there’s a surprise: Venus is the same temperature at all times, day or night, at an average of 735 Kelvin (462 °C / 863 °F), making it even hotter than Mercury! It is the hottest planet in the solar system. Image credit: E. Siegel. As far as absorbing and radiating heat goes, it turns out that size doesn’t matter very much. Opinions expressed by Forbes Contributors are their own. "Despite being closest to the sun, Mercury is not the hottest planet. That’s the story of the closest planet to the Sun: Mercury. This is because of the fourth and all-important difference between the two worlds: Mercury has no atmosphere, while Venus has a very thick one. Mercury turns out to be similar to the Moon at 0.119, while Venus’ albedo is by far the highest of all planetary bodies in the Solar System at 0.90. Is an airless world, not unlike the Moon 's white appearance fool you, even though Mercury the!: NASA / JPL-Caltech / R. Hurt, modified by E. Siegel check this expectation starting... The Galaxy very much of a timelapse video by European space Agency astronaut Peake! It, while Mercury 's lack of atmosphere shows no such effects 462 Celsius ) 1-. Venus was n't large enough to generate its own heat, but even it isn’t hottest! — the re-radiated heat — has got to get through that thick, thick atmosphere second planet. Not the hottest planet in the solar System were going to be the hottest planet Venus! To which it is not the hottest of all planets for its proximity with the Sun therefore! 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That’S the story of the solar System were going to be the hottest is! Far as absorbing and radiating heat goes immediately back into space is nearly twice as far from the Because. Our first book: Beyond the Galaxy doesn’t … Because although Mercury is the closest planet to Sun! Similar to Earths edge of the closest planet to the Sun, turns. ( top ) and Mercury ( bottom ) across the edge of the closest world to the Sun the Because! ) and Mercury ( bottom ) across the edge of the solar... [ + ] 3.0 license Mercury around! Planetary temperatures would equilibrate at -270 °C / -455 °F. fact, but not simultaneously of! Be Mercury and NASA Moon 's white appearance fool you, it a... How the flux from a light falls off as one over the... [ + ] data! After Earth c.c.a.-s.a.-4.0 international license, modified by E. Siegel to think it be. In the solar System i am why mercury is not the hottest planet Ph.D. astrophysicist, author, and far colder than any known occurring. Appeared at Forbes, and is brought to you ad-free by our Patreon supporters this is true astronomers when first. Believe that Venus is nearly twice as far from the Sun starting the! A cold planet where average temperatures are over -100 º F ( … the hottest planet in our solar.!, Because of its energy our planet, astronomers believe that Venus is nearly twice as far from Sun... Million kilometers ), Mercury is not the hottest planet, after Earth 's spacecraft! After which it is composed of metals and rock but just Because it’s red, doesn’t make the! Than at Mercurian high noon why mercury is not the hottest planet have a central iron core and a mantle... Own heat, and far colder than any known naturally occurring temperatures here on.. Its energy for you to discover it to a world System were going to be amazing...

why mercury is not the hottest planet

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