Vesta, the brightest asteroid, will be at opposition – the middle of the most favorable time – on Thursday December 21.
Here is the sky scene for an American location as Vesta comes up into view over the evening horizon.
The sunset time at this location is a few hours after the instant of opposition. Vesta’s track is shown over 5 days; you can see that it is retrograding (moving westward), as planets do when we overtake them on the inside; and that it has just passed the point we mark as the “anti-Sun”, or direction opposite to the Sun. And that all this takes place near the June solstice point, or northernmost point on the ecliptic. Vesta is traveling the northerly part of its orbit, so this is a favorable opposition for north-hemisphere observers.
But how findable is it? Its magnitude of 6.4 is bright for an asteroid, but hovers around the naked-eye limit. So it is dimmer than many stars not shown in the horizon scene, and finding it requires good sky conditions and studying, with binoculars or small telescope, the star field as shown in this detail of the chart on page 129 of Astronomical Calendar 2023.
To quote from the “asteroids” section of the book::
4 Vesta, though only the 4th asteroid discovered, is the second largest, slightly wider than Pallas but considerably more massive. It is the brightest almost always (Ceres when brightest is 0.1 magnitude brighter than Vesta when faintest). This results from a combination of size, distance … and high “albedo” or reflectivity—that is, Vesta has a light-colored surface. It is aptly named for the Roman goddess of the hearth.#
In 2023 Vesta continues to travel behind, south of, and outside of Juno. … As we overtake it, its retrograde path takes it from Gemini back into Taurus. At opposition on Dec. 21, it should reach magnitude 6.4: findable by the naked eye in good conditions. It can be as bright as 5.3, as in 2018 June and 2029 July, but is close to its dimmest opposition magnitude of 6.5 as in 2019 Nov. and 2030 Nov., because it was at aphelion in October.
Vesta’s path in space, with sight-line from Earth to the asteroid at the time of opposition, is shown in this detail from the space view on page 127 of the book.
Procrastination Department
I was going to prattle about the Vestal Virgins, and about Vesta matches. But it’s been long enough, we’ve had a power outage and had to live by candlelight for several hours, and – basta. Another day.
Thank you Guy. Vesta is my favorite asteroid, simply because it’s the brightest. I’ve been enjoying following Vesta through 10×42 image-stabilized binoculars since September. As Vesta has gotten brighter and now appears to move faster against the stars as she approaches opposition, it’s easy and fun to track her motion from one night to the next, although for the past few nights we’ve had clouds and welcome rain, and we may be clouded out on the night of opposition.
In 2011 – 2012, Vesta was visited and orbited by the Dawn spacecraft, which then went and orbited Ceres. (Dawn is the only spacecraft to orbit two different bodies, unless you count craft that that were launched into Earth orbit and then sent to the Moon or beyond.) Dawn discovered that Vesta, with a diameter of 525 km, has a 400 km impact basin! I imagine such an object would be shaped like a bowl, but that’s not how Vesta looks in the Dawn images. The north pole is a little flattened and the south pole has a noticeable bump on it, but overall Vesta looks more like a rock than a bowl. The huge Venenia impact basin and Rheasilvia crater are centered on the south side of the asteroid, so apparently the bump, which is actually a 20 km high mountain (higher than Everest, almost as high as Olympus Mons!), is the central peak in Rheasilvia crater. This asteroid has some crazy topography!
https://trek.nasa.gov/vesta/# shows various 2D maps and a 3D globe that you can spin around, with interesting layers you can paste over the maps or the globe. The geology layer is informative.
Happy holidays! It is better to light a single candle (with a Swan Vesta!) than to curse the darkness.
Thank you, Anthony, for adding all that extra information and appreciation about the white asteroid!
Your “prattle” is profound to me. Speaking of chattering, Roger Waters does a lot of that on his new album, “Dark Side of the Moon Redox”.