Last month Vesta reached opposition and and it’s still very visible and not (visually) too far from Saturn. This is a monster asteroid and was visited by NASA’s Dawn spacecraft back in 2011. It makes up about 9% of the entire mass of the asteroid belt so is one of the more significant asteroids in the Solar System. Vesta has a large crater that is about 460km across and it’s one of it’s defining features given the huge size of this impact compared to the size of the actual asteroid at around 530km. This crater occurred in the early life of the asteroid and ejected many smaller asteroids, called vestoids, into the asteroid belt and a bunch of them hurtled their way towards the Earth and created havoc here.
Vesta is a bit like a tiny planet, it has a core, a mantle and crust. The core is most likely nickel and iron and the crust probably formed pretty quickly. The Dawn spacecraft’s visit allowed us to get a really close look at this asteroid and determine some of the characteristics of its formation, including some signs of volcanic activity on its surface. Another defining feature of the asteroid is the huge mountain near the South Pole. This mountain reaches about 20km above the surface of the asteroid making it one of the largest mountains in the Solar System. The examination of the surface of Vesta also showed possible evidence of past water activity and scientists believe that there may be water buried deeper in the crust, some of it delivered during the many impacts the asteroid has suffered from.
Given that Vesta has only just past opposition it is still very much visible and only just a bit dimmer than a couple of weeks ago so still worth grabbing your telescope or binoculars and having a look at this spectacle from the Asteroid Belt. At the moment Vesta is about 175 million kilometres away and getting further away everyday, in a week it will be nearly 180 million kilometres away. At the moment it’s located between Saturn and M9, roughly, and is about 5.7 in magnitude so just a little beyond naked eye viewing but well within the capabilities of telescopes and binoculars. Being smack bang in the middle of the Milky Way it might not be too easy to spot, unless you live in a light polluted area where the dimmer stars won’t be a problem so it will stand out a bit more.
I think the easiest way to spot Vesta is to first find Saturn, which is conveniently in Sagittarius at the moment, and is very easy to spot because it’s so bright, it’s also next to an amazing array of nebula and other wonderful deep sky objects that will distract you on your search for Vesta.
The basic way of finding the asteroid at the moment is to line up Saturn with the star Xi Ophiuchi, which is about 4.4 in magnitude. It can be found be going a bit to the right of the bright star Sabik (about 5 degrees), also in the elaborate constellation of Ophiuchus.
Now if you imagine a line between Xi Ophiuchi and Saturn, follow along this line until you locate the brightest star on the line – about 2/5 of the way towards Saturn (also about 5 degrees). This star is called 58 Ophiuchi and is a bit dimmer than Xi Ophiuchi at about 4.9 magnitude. Now, if you imagine a line between these two stars then just about half way between them you will find Vesta.
The good news is that Vesta keeps tracking towards Xi Ophiuchi for the next few days before starting a wide turn to the right taking it back towards Saturn, on a line between Theta Ophiuchi and Saturn.