Vesta at its Opposition Will Announce the Solstice

Vesta, the brightest asteroid visible from Earth, will soon reach its opposition on December 21. This date coincides with the solstice, a biannual natural event during which the sun reaches its maximum or minimum declination. Although Vesta does not impact Earth’s seasonal variations, this alignment provides a unique opportunity to explore the complex dynamics of asteroids and deepen our understanding of our planet’s movement and its implications.

The December solstice is known for an interesting trait: it provides the longest night of the year for the people in the northern hemisphere, while those in the southern hemisphere enjoy their longest day.

The Earth’s axis is tilted at an angle of 23º27′, a feature which, combined with its orbit around the Sun, results in fluctuations in insolation—the quantity of sunlight reaching the planet—across the hemispheres throughout the year.

Vesta also completes an orbit around the Sun – taking approximately 3.63 years – while consistently following a stable trajectory within the Main Belt, posing no threat to Earth. During a specific phase of this orbital journey, the asteroid approaches our planet more closely, creating favourable conditions for observation. This favourable alignment happens roughly every 17 months, with the next occurrence expected to take place in May 2025.

Orbits of Earth and Vista highlighted. On December 21st, the Sun, Earth, and Vesta will be aligned in space. This position will allow a better observation of the asteroid (Space Reference).

Vesta can be observed using binoculars and small telescopes, and under certain circumstances, it may even be visible without the aid of any instruments. However, its current distance from the Sun, known as aphelion, is preventing it from exhibiting the usual increased brightness that enables naked-eye visibility.

Vesta’s trajectory a few days before and after its opposition. The deep sky object NGC 2175 could help identify the asteroid (in-the-sky.org)

Nevertheless, Vesta is presently passing through an intriguing area of the night sky, crossing paths with the constellations of Orion the Hunter, Taurus the Bull, and Gemini the Twins. In this celestial panorama, the deep sky object NGC 2175— commonly known as the Monkey Head Nebula among astrophotographers, and consisting of both a star cluster and a nebula, will be in close proximity. This can serve as a useful guide for observers to locate the asteroid.

Asteroids are not easily recognisable from Earth in their conventional depictions, as they can resemble potatoes. Sometimes, their appearance can be mistaken for stars, so it is important to remain vigilant. To accurately distinguish them, it becomes essential to track their position over several days using sky maps. This method allows observers to identify the asteroid’s movement relative to the fixed positions of surrounding stars, facilitating accurate identification.

Animation made with Vesta images taken on different days, showing its movement compared to the stars in the background. (Urban Astrophotography)

See also:
LEARN – When is the best time to observe an asteroid?