Have you ever seen an asteroid with your own eyes? If not, now through March presents an excellent opportunity to find Vesta, the brightest. In fact, it's just bright enough to glimpse without optical aid from rural skies. I've seen it faintly on a couple occasions, but it's much easier to spot in binoculars. Even from the suburbs a pair of 7x35s will coax it into view.

(From left) The sizes of Vesta, Ceres and the moon are shown to scale. (Moon: Gregory H. Rivera, others: NASA / JPL-Caltech, UCAL, MPS, DLR, IDA)
(From left) The sizes of Vesta, Ceres and the moon are shown to scale. (Moon: Gregory H. Rivera, others: NASA / JPL-Caltech, UCAL, MPS, DLR, IDA)

Vesta reaches opposition on March 4, when it's closest to the Earth and shines brightest. Bright is always a relative term in astronomy, but for an asteroid, Vesta delivers. It's one of the few of its kind visible without optical aid, peaking at 6th magnitude, the naked-eye limit, from a dark sky. On opposition night it rises in Leo the lion at sunset and remains visible until dawn. But don't wait until then for a look. Vesta will be binocular-bright for at least a month.

Vesta orbits the sun just like the planets. It's located a bit beyond Mars in the main asteroid belt and currently about 129 million miles (208 million km) from Earth. A day on Vesta zips by in just 5.3 hours, but a year lasts 3.6 Earth years. Since age is determined by how many times we've been around the sun, I'd be a youthful 18 in Vestan years. Who am I kidding?

To find Vesta, first locate Leo's brightest star Regulus. You can use the Bucket of the Big Dipper to help guide you to the star. Vesta is near Denebola in the lion's tail. (Stellarium)
To find Vesta, first locate Leo's brightest star Regulus. You can use the Bucket of the Big Dipper to help guide you to the star. Vesta is near Denebola in the lion's tail. (Stellarium)

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Vesta spends the next month tracking west across the lion's tail. Two brighter stars — second magnitude Denebola and third magnitude Chertan — help to point the way. You can start as early as 8 p.m. but Vesta will be higher and easier to see by 9. First, find Leo's brightest star, Regulus. Face east around 9 p.m. and look about four fists or almost halfway up the sky for a single bright star. You can also enlist the help of the Dipper Bowl to point you to Regulus.

Once you've identified Regulus, hold your fist at arm's length diagonally against the sky, and drop down a little more than two fists to the left to Denebola, Leo's second brightest star. Its name means "tail of the lion" in Arabic.

Once you've located Denebola, point your binoculars at the star and slide to the upper right to find a trio of similarly bright stars in a bent line. Use them as well as Chertan and Zosma to keep track of the asteroid as it moves westward across Leo this month and next. (Stellarium with additions by the author)
Once you've located Denebola, point your binoculars at the star and slide to the upper right to find a trio of similarly bright stars in a bent line. Use them as well as Chertan and Zosma to keep track of the asteroid as it moves westward across Leo this month and next. (Stellarium with additions by the author)

Point your binoculars at Denebola and focus sharply, then slide about one binocular field of view (about 5°) to the upper right. Look for the three stars labeled "Star trio" on the map. They're all about the same brightness and line up vertically one above the other. Vesta lies just to the right of this trio through the end of the month as it heads toward Chertan.

I've marked the asteroid's position every five nights. To find out where to look on a particular night, just interpolate between the dates. Be sure to return a few nights later for a second look (or a third or fourth!), and you'll see how it moves just like a planet.

Not only does Vesta's large size (329 miles / 530 km diameter) set it apart from most main belt asteroids, but it's the solar system's only known protoplanet. Unlike most asteroids, which are composed of a mishmash of material, Vesta is differentiated or layered with a metallic core wrapped in a dense, rocky mantle and topped by a crust of cooled lava. Earth has a similar build.

Five billion years ago, an enormous cloud of gas and dust shrank under its own self-gravity to form the sun at its center. The rest of the material spread into a disk. Fragments of rock and ice gathered through friction and gravity to form asteroids and protoplanets, some of which coalesced into planets. Smaller bodies became asteroids and comets. (NASA)
Five billion years ago, an enormous cloud of gas and dust shrank under its own self-gravity to form the sun at its center. The rest of the material spread into a disk. Fragments of rock and ice gathered through friction and gravity to form asteroids and protoplanets, some of which coalesced into planets. Smaller bodies became asteroids and comets. (NASA)

Astronomers speculate that if it wasn't for Jupiter's gravity agitating the asteroids between itself and Mars, Vesta may have grown into a full-fledged planet. Pity, it only made it halfway, but that's exactly what makes it unique. We know this and much more about Vesta thanks to NASA's Dawn spacecraft, which entered orbit around the protoplanet in 2011.

For 14 months it took a ton of photos and gathered information on both its outer crust and deep interior. Dawn confirmed that a class of meteorites found on Earth called Howardites, diogenites and eucrites — together known as the HED clan — derive from Vesta and were released willy-nilly into space in the wake of at least one major impact.

This is a slice of the eucrite meteorite NWA 2724 found in the Sahara Desert. It was once part of a lava flow on the surface of Vesta. After the lava cooled, an impact sprung it free and it eventually landed on the Earth as a meteorite. (Bob King)
This is a slice of the eucrite meteorite NWA 2724 found in the Sahara Desert. It was once part of a lava flow on the surface of Vesta. After the lava cooled, an impact sprung it free and it eventually landed on the Earth as a meteorite. (Bob King)

Vesta looks like a point of light even in a large telescope, but the more you learn about this special object the more you bring to the experience of seeing it for the first time. Moonlight from the waxing gibbous and then full moon will temporarily make it difficult to spot the asteroid between Feb. 26-28. But before and after that time, it should be easy to see and follow in binoculars or a small telescope.

Happy hunting!

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.