If you have been keeping an eye on the night sky recently, you may have seen Jupiter rise earlier and earlier each evening and become brighter than all of its stars. This is because Jupiter has reached its closest approach to Earth – known as its perigee – for 2023.
People tend to misperceive Venus as being closest, when in reality Mercury is closer. With its rich history and mysterious features, Mercury makes for an intriguing space exploration destination.
Mercury
Mercury is one of the nearest planets to Earth and can easily be seen with binoculars when high in the sky before dawn. Mercury currently forms part of what’s known as “5 planet alignment”, along with Mars, Jupiter, Saturn and Venus.
Mercury is made up of an iron core and rocky outer shell. Without an atmosphere to speak of, its grey surface is covered in impact craters – these giving rise to brilliant streaks in the night sky known as crater rays as their fine particles of crushed rock are more reflective than surrounding material and emit an amazing flash of white light when they explode upon an impact.
As Mercury orbits the Sun, it moves closer and further away from it, giving scientists a unique opportunity to test theories about gravity while also explaining why Mercury spins so slowly compared with Earth days; one day on Mercury lasts roughly 59 Mercurian sidereal days or 176 Earth days; but one year is accomplished in just 88 Earth days!
Due to its proximity to the Sun, Mercury does not possess a dense atmosphere; instead it boasts a thin exosphere made up of atoms blasted off by solar wind and meteoroids – including oxygen, sodium, hydrogen, helium and potassium with trace amounts of carbon dioxide, water nitrogen xenon and krypton.
People often mistake Venus for Earth’s nearest neighbor; in reality it’s often Mercury. Although Venus might come closer occasionally due to how distance is defined between planets, scientists developed a new method that takes into account each planet’s orbit size to show that on average Mercury is closer than any other planet.
Mercury can be seen occasionally appearing in the evening sky this month. It’s currently at its greatest elongation east, which means it is currently separated from the Sun by roughly half as much. Mercury will next come close to conjuncting with it in late April when Mercury will appear hidden behind it in the morning sky.
Venus
Venus, the second planet from the Sun and sixth in size, is our nearest neighbour by far. She shines brighter than the Moon in the evening sky and thus had great significance to ancient cultures around the globe.
Venus orbits very close to that of Earth, which explains its brighter light output and why it can only be seen near sunrise and sunset; otherwise it wouldn’t be visible during midday hours.
At low-Southern latitudes, Venus rises 2 1/2 hours before the Sun. At this time its altitude reaches its maximum eastward position of just under 30deg while its apparent diameter reaches its smallest value. At high-Northern latitudes the apparition ends on November 17th when Venus will have just crossed 20deg south of its position on November 10th.
At 0012 UT on December 11th, the planet passed 7 degrees 8 minutes north of Fang (Scop or Pi Scorpii mag. +2.8), situated within Scorpius the Scorpion. Later that same day at 1820 UT it passed 14deg 0 minutes north of Dschubba (Scop or Delta Scorpii mag +2.3). Both stars lie within Scorpius.
On January 24th Venus will graze the Lagoon Nebula (M8 or NGC 6523). This event can be seen through any telescope, especially larger ones equipped with nebulular filters. This spectacular sight occurs at dusk and can be seen across South-Western Australia spanning From Onslow to Karlamilyi National Park.
Engineers affiliated with NASA and Los Alamos National Observatory conducted computer simulations of the Solar System over thousands of simulated years to see which planet was closest to which. Based on this, Mercury proved closer than Venus due to the way that its orbit compared with those of other planets.
Mars
Mars can currently be found in Aquarius and can be seen at dawn for observers at latitudes south of about 40o North. At its closest approach to Earth in its orbit, it appears as a brilliant red beacon in the sky – best seen using a telescope; though if clear skies allow for it, even naked eye viewing can provide great enjoyment! This conjunction will last approximately six and half months as Mars travels around our Solar System on its elliptical orbits.
When asked which planet is closest to Earth, most will incorrectly name Venus due to its closeness (about 0.28 AU or 25 million miles). But this misperception isn’t solely the result of ignorance.
Problematically, however, these calculations only account for distance and not time; since all planets orbit on elliptical paths that do not spend much time close by one another. Astronomers like Mark Stockman use computer simulations to gain a clear picture of which planet is closer than expected over an average 10,000 year time period.
This data indicates that Mercury is currently the closest planet to Earth on average; however, this doesn’t provide a full answer, since Venus would likely be closer to us on average than Mercury if all planets lined up along one side of the Sun.
Add further confusion by considering that Mars and Venus can sometimes come close together, creating more variables than expected in any one year’s average; so on some occasions, Mars can actually become Earth’s closest planet.
Mars can next be seen with clarity in late March 2022 when its orbit comes close to our own. At that time, it will shine at its brightest as it rises from the East around an hour and a quarter before sunrise, well worth taking time out to look. When using a telescope you should be able to spot all major features including Syrtis Major and its Northern Polar Region.
Jupiter
Contrary to Mercury and Venus, Jupiter can always be seen. Its most prominent days occur during opposition – typically lasting about one month each year – rising low in the east when the Sun sets and dominating Aries constellation as seen from Earth. Tonight Jupiter will again reach opposition, staying visible until dawn before gradually retreating away again over time.
Planet Jupiter and its nearly 70 moons continue to capture our interest, too. Ganymede, larger than Mercury, boasts its own magnetic field and features volcanoes which spew out clouds of yellow sulfur 300 miles (500 kilometers) high. Meanwhile, scientists believe frozen Europa may conceal an ocean hidden under its icy crust; scientists hope to discover whether life could exist there too.
Jupiter produces vast amounts of radiation–more than 1000 times greater than humans can tolerate–but this radiation is effectively blocked by layers of gases encasing its core, covering an area spanning 44 miles (71 kilometers). The outermost layer may consist of ammonium hydrosulfide crystals and water ice; middle-level layers likely consist of hydrogen, nitrogen and oxygen mix; while innermost layer may consist of water vapor or chemicals yet to be identified.
Watch Jupiter’s largest moon, Ganymede, undergo an impressive eclipse tonight starting around 10:30 P.M. EST. Look for Ganymede near Jupiter’s northwestern limb; as soon as it fades from view into Jupiter’s shadow it should reappear on its northeastern limb a short while later.
Now is an excellent time to view Jupiter through a telescope, especially those equipped with modest scopes. Even modest scopes can reveal Jupiter’s light and dark cloud belts as well as the Great Red Spot which looks like an enormous eye peeping out from amongst the swirling vapors. Jupiter’s reddish atmosphere comes from its mixture of helium and carbon dioxide molecules while its turbulent center generates winds reaching 335 miles an hour at its equator – creating this great red spot!