People often wonder which planet in our Solar System is closest to Earth; however, the answer can change over time depending on where each planet sits in its orbital path.
On average, Mercury overtakes Venus and Mars as our nearest planet neighbor; however, this order varies significantly over time.
Venus
Venus, our nearest planetary neighbor, has long been of interest to scientists. With an atmosphere composed mainly of carbon dioxide – and 90 times thicker than that on Earth – and receiving two times more solar energy from its Sun source than Earth does, Venus experiences extremely hot temperatures. Early telescopic observations suggested it might once have been warm and wet like Earth; however modern research indicates this was never true: Venus’ climate is so harsh, dry, and forbidding that life wouldn’t survive long term there.
Venus orbit is significantly less eccentric than that of Earth (hence its proximity), making its passage across in front of the Sun more frequent than Earth and therefore becoming less visible to us during these transits. These passages occur approximately every 584 days and mark what’s known as inferior conjunction with the Sun; following which Venus becomes visible again for approximately 263 days during morning apparition, reaching its farthest West point – known as its greatest Western elongation – before becoming invisible again behind it again.
On October 23rd at 1452 UT, Venus will reach its maximum Western elongation for 2017. At very low Southern latitudes, observers should see it rise two hours prior to sunrise while those at mid-Northern latitudes could witness it rise as early as four hours prior.
Next evening, Venus will pass just 1o.9 south of Dabih (Cap or Beta Capricorni, mag. +3.0v). This variable star can be seen through binoculars and small telescopes and forms an isosceles triangle close to dusk that’s visible during dusk hours.
Venus will also pass within 2o North of NGC 6523, more commonly known as the Lagoon Nebula – creating an eye-catching sight, especially with larger telescopes with filters dedicated to viewing this magnificent phenomenon.
Mercury
Mercury is the smallest planet in our Solar System and closest to the Sun, making it difficult and challenging to see. Because of this proximity, its orbit never takes it far enough from us so it can only be seen at dawn or dusk or during its maximum western elongation on 25 October.
Planet Mars features a thin and hot crust over a dense iron core. Its surface is marked by numerous impacts during and after its formation; these range from bowl-shaped cavities to vast multi-ringed basins up to one thousand kilometers across. However, unlike on the Moon, its lack of atmosphere prevents smoothed-over craters being filled in by lava flows.
Mercury shines brightest at night when reflecting sunlight back from Earth; during the day its temperature makes it less dazzling; unlike the Moon however, Mercury lacks an atmosphere and so the Sun heats directly from below, creating an unequal temperature gradient between its equator and poles.
Astronomers have recently discovered that Mercury’s surface contains volatile elements such as sulfur and sodium. This suggests that, in addition to water ice discovered via radar at its poles, Mercury may once have been warmer and wetter. Their presence can help us disprove some theories regarding its formation.
Mercury may be small and slow moving, yet still boasts an impressive magnetic field that extends about 1.1% of Earth’s strength – its dipolar magnetic poles almost perfectly aligning with the planet’s spin axis.
Mercury’s proximity to the Sun has provided additional evidence for Albert Einstein’s theory of special relativity. From Mercury, due to gravity effects, the Sun appears three times bigger than from Earth.
Mars
Though Mars may not appear as dramatic when observed through a telescope as Venus or Mercury, it remains an interesting planet to study. Telescope users will be able to witness features on this red-orange planet like its polar ice caps and massive dust storms; under certain conditions they may even spot two small moons named Phobos and Deimos after horses used by Mars in his war chariot.
Just like Earth, Mars is a solid planet made up of a rocky mantle composed of iron and nickel with an outer layer composed of basalt. The surface features low-lying plains, high mountains, rolling terrain and volcanic plateaux; Olympus Mons is its tallest volcano located near its southwest corner on Mars.
Astronomers have learned much about Mars since the first probes landed there. They’ve discovered that once upon a time it was warmer and wetter; liquid water may even have flowed there at one point in history. Mars shares many characteristics with Earth in terms of early history and so any steps leading to life on our planet might also have happened there.
Mars orbit is more elliptical than our own planet’s, bringing it close to Earth at certain points over time. This closeness can also be affected by other planets’ gravitational pull – particularly Jupiter – altering Mars’ orbit shape, leading to 26 months of “Mars Close Approaches,” when Mars comes close enough for human beings to perceive.
Astronomers know this is an opportunity to observe this fascinating planet, but selecting an ideal night for this task is crucial to getting optimal viewing results. When done poorly, Mars appears as a massive orange ball; on good nights however, it transforms into its own little world!
Proxima Centauri
Proxima Centauri lies less than four light years away from Earth and may host an Earth-like planet with water and an atmosphere. Scientists announced their discovery of Proxima b – a rocky planet orbiting Proxima with a minimum mass of approximately 1.3 Earth masses that orbits with an semi-major axis of 0.05 astronomical units – in August 2016. Scientists named this habitable zone planet Proxima b as Proxima B.
Telescopes used the radial velocity method to locate Proxima Centauri using its stellar gravitational pull on light from nearby stars, measuring how its light changes with distance from it and any associated planets. Astronomers measured variations in starlight frequency due to factors like stellar activity or flaring which made detecting Proxima Centauri particularly challenging; their signal had to be detected through extremely frequent flares to be found – something published in Nature on August 24.
Proxima b is the closest known exoplanet to Earth and could provide an ideal environment for extraterrestrial life. Located closely to its parent star, Proxima could become tidally locked – always facing one side towards it while the other reflects off space – possibly as early as next century. Furthermore, Proxima may emit intense UV radiation that depletes Proxima’s atmosphere quickly of water molecules essential for life on Proxima b.
Scientists hope to study Proxima Centauri further by gazing directly upon it. However, that will prove challenging since its light is so faint it would likely be overwhelmed by nearby stars even with powerful telescopes like Hubble Space Telescope. Instead, researchers must wait until 2024 when more advanced telescopes will become available in order to conduct direct imaging of Proxima Centauri and its nearby planets.
Astronomers will study this exciting new world to answer numerous questions, such as whether or not it has an atmosphere, its size and surface features. But simply finding such an environment in our solar neighborhood marks an impressive milestone that could transform how we understand both universe and ourselves.