It’s time to equip yourself with gloves, scarf and hat to face these cold winter evenings and enjoy the spectacle ofopposition of Mars in the night between 15 and the January 16th. At 2:17in fact, Mars will be found from opposite side of the Earth from the Sunwith the three bodies forming an imaginary straight line in space. This geometric configuration of opposition maximize the number of hours in which Mars will be visible, so much so that it will rise in the east exactly in conjunction with the setting of the Sun, remaining visible for the rest of the night. The red planet will be in the constellation Gemini aligned with its two brightest stars, Castor and Pollux.
At opposition Mars will reach the magnitude of –1.4, i.e. it will as bright as Siriusthe brightest star in the sky. The event will be visible to the naked eyewith Mars easily recognizable as a bright reddish star heading east at sunset. Mars’ opposition follows its own by only 4 days closest approach to Earth on January 12so it will appear very large angularly in the sky. There next opposition of Mars will be the February 19, 2027while to have a similar situation in terms of angular dimension we will even have to wait until 2031, so the event is definitely not to be missed!
Where and when to observe the opposition of Mars
The exact moment Mars will be at opposition will occur at 2:17am on January 16, 2025. Already during the previous nights, as well as in the immediately following ones, Mars will put on a show by appearing as a brilliant reddish star that crosses the sky throughout the night. The orbital configuration of the opposition means that Mars has the maximum visibility during the nightsince it rises coinciding with the setting of the Sun.
January 15th Mars it will rise in an east-northeast direction around 5pm. On these evenings the planet is in the constellation Geminivery close angularly to the two brightest stars of this constellation, viz Castor and Pollux. During the evening the red planet will rise higher and higher on the horizon, reaching the maximum height of 73° at the passage through the local meridian around half past midnight.
At the exact moment ofopposition Mars will shine with one magnitude equal to –1.4similar to that of the brightest star in the sky, Sirius. The red planet will be at opposition at a height of 61° on the horizonin west-southwest direction. To find it you can use the star Sirius or the constellation of Orion, using them as a reference to find Mars simply by looking up from the latter. Even the Moon, which has recently passed the full Moon phase, can lend you a hand. You will find Mars to the right of the Moon like a brilliant reddish star in the company of the stars Castor and Pollux.
How to observe the opposition of Mars
In Astronomy a planet is in opposition when the angle formed by the imaginary lines connecting the planet to the Earth and the Earth to the Sun is 180°. In this geometric configuration, the planet is located in direction diametrically opposite to the Sunso it will rise when the Sun sets, remaining visible throughout the night.
The oppositions are therefore the best time to observe the planets outside Earth’s orbit and Mars is no exception, with an opposition rate of approximately two years. The opposition of January 16th is particularly favorable since only a few days earlier, the January 12thMars has reached the minimum distance from Earthequal to approximately 96 million km. The concomitance of these two events makes the angular size in the Martian sky particularly high, equal to approximately 14.6 arcseconds. To be able to have such a high value again we will have to wait until 2031.
Although Mars is especially large during opposition, and this may be observed well with the naked eyethe angular size is however still too small for our eye to see the details of the Martian surface. For this reason, to see any detail on Mars, even in opposition, we will need at least a medium-sized telescope, an eyepiece that magnifies by about a factor of 100 and a night of good visibility.
