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Astro Bob: Have a small scope? Take a peek at Hebe

The asteroid Hebe is passing through the teapot-shaped constellation Sagittarius. Although a bit faint for most binoculars you can easily spot it in a small telescope.

Hebe locator wide S2.jpg
The bright asteroid Hebe is located just above the Teapot asterism that forms part of Sagittarius the Archer. It slowly tracks to the southeast now through fall. To get oriented, start at Saturn to point you to the general vicinity, then use the more detailed map below to star hop to the asteroid. Contributed / Stellarium with additions by Bob King

Thousands of known asteroids ply the summer nighttime sky. But only a dozen or so are currently bright enough to spot in a small scope. One of the easiest is 6 Hebe (HEE-bee) with a diameter of about 116 miles (186 km). It orbits the sun every 3.8 years at an average distance of 228 million miles (367 million km). That places it squarely in the main asteroid belt between Mars and Jupiter.

The number "6" in front of Hebe's name tells us that it was the sixth asteroid discovered. German amateur astronomer Karl Ludwig Hencke found it the night of July 1, 1847. Around the time of its discovery our understanding of these small objects was in transition. Originally considered planets, astronomers eventually reclassified them as asteroids, a Greek word that means "star-like," as their numbers grew.

Asteroid belt with Ceres Vesta NASA_McREL.jpg
This artist illustration depicts the main asteroid belt between Mars and Jupiter, home to Hebe as well as Ceres and Vesta, the two largest asteroids in the belt. Contributed / NASA, McREL

If you've never seen an asteroid before, that's exactly what one looks like in a telescope — a stellar point! In contrast, planets have plainly visible shapes. Today there are more than 1.1 million known asteroids. Astronomers estimate the main belt is home to between 1.1 and 1.9 million asteroids larger than 1 kilometer (0.6 miles) in diameter, and millions of smaller ones. And yet if you packed all those objects into a single ball of rock it would be smaller than the moon.

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Hebe orbit.jpg
This map shows Hebe's location along its orbit, shown in white, on Monday, August 23, 2021. Notice that the asteroid's orbit is tilted with respect to the planets. Contributed / NASA HORIZONS

Hebe is one of the larger asteroids, which also makes it one of the brightest. When closest to the Earth and sun it can reach magnitude 7.5 and be seen in binoculars. This observing season it's a little fainter, around magnitude 8.9 at the moment. That still makes it an easy catch, but most of us will need a small scope.

Hebe hangs out in Sagittarius now through the end of October as it slowly arcs to the southeast. You can hunt for it as soon as it gets dark, starting around 9:30-10 p.m. local daylight time. The asteroid remains well-placed for viewing until midnight. You might already be familiar with the Teapot asterism, but if not, start at Jupiter and Saturn, the two bright "stars" low in the southeastern sky. From Saturn, look two-and-a-half fists or 26° to the right to find the 2nd magnitude star Nunki in the teapot's handle.

Hebe August 23.jpg
This more detailed map zooms in on Upsilon, Rho-1 and Hebe. Stars are shown to about magnitude 9.5. The position of the asteroid is marked at 3-day intervals at 10 p.m. CDT. If you're in another North American time zone, the positions will still be very close to the ones shown here. Contributed / Stellarium with additions by Bob King

About 5.5° or one binocular field of view to the upper left (northeast) of Nunki you'll see a flattened triangle of stars, the brightest member of which is Pi Sagittarii. Another 5° or so in the same direction will take you to a dimmer pair of stars, Upsilon and Rho-1. Use a low magnification eyepiece (about 35-50x) and point your telescope at this pair, then star hop to Hebe with the aid of the detailed map.

I like to connect the asteroid with neighboring stars into a shape, say a triangle or box. If the pattern matches the position of the asteroid as shown on the map then I've nailed it — Hebe is mine! Once found, you can track it nightly or look every few nights to watch the object slowly move through the background starfield as it orbits the sun. I liken it to a ride-along.

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Meteorites H5 chondrite NWA 2710 S Hebe.jpg
This slice of the H5 chondrite NWA 2710 may be a piece of Hebe. It glitters with specks of iron-nickel. Contributed / Bob King

Astronomers can measure the approximate composition of an asteroid by studying the light it reflects from the sun. In the case of Hebe we've learned that it's an excellent match to two types of meteorites found on Earth — the common H-chondrites, which are stony meteorites with a high metal (H) content, and the less common IIE iron meteorites, which may have been melted out from Hebe when the asteroid was heated by earlier impacts.

Since H-chondrites are easy and relatively inexpensive to acquire through meteorite sellers like the Meteorite Market or Polandmet , it's entirely possible to own a piece of Hebe while at the same time observing it in the telescope.

Hebe VLT ESO.jpg
These images of 6 Hebe were taken with the Very Large Telescope located in the Atacama Desert in northern Chile and show possible craters on its surface. Contributed / ESO, VLT

You might wonder about the origin of the asteroid's name. Hebe was the ancient Greek goddess of youth. Among her talents was the ability to restore youth to mortals, yet another excuse to track down this delightful asteroid the next clear night.

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

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at nightsky55@gmail.com.
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