See The Dwarf Planet Ceres In Binoculars

Asteroid 1 Ceres beckons binocular-toting skywatchers the entire month of June as it travels from Ophiuchus into Scorpius not far from Jupiter. Ceres is a dwarf planet and the only one that’s easy to see. It’s currently 163 million miles (263 million km) from Earth. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

There are only five dwarf planets: Ceres, Pluto, Eris, Makemake and Haumea. Of these, only one is visible in anything other than a chunky telescope — Ceres. And you can see it this month in nothing more than a pair of binoculars. I stood in the driveway two nights under under a smoky sky and spotted it in my 8x40s near the head of the scorpion. You can, too.

Ceres was the first asteroid discovered, way back in 1801, and the largest object in the main asteroid belt between Mars and Jupiter. Astronomers reclassified it as a dwarf planet in 2006 along with Pluto and three other large but remote asteroids in the Kuiper Belt beyond Neptune. Dwarf planets lie somewhere between asteroids and planets. They’re big enough for self-gravity to have compressed them into spheres, and they orbit the sun (and not other planets) but lack the gravitational might to clear their orbits of other asteroids.

Ceres describes a short arc near Graffias (a.k.a. Beta (β)Scorpii) this month and shines around magnitude 7, an easy sight in binoculars from a reasonably dark sky. Positions are marked every 3 nights for 10 p.m. CDT. Because the dwarf planet moves relatively slowly, the positions are good for all North American time zones. Stars are shown to magnitude 7.5. Chris Marriott’s SkyMap with additions by the author

At 588 miles (945 km) across Ceres is about as big as Texas or a quarter as wide as the full moon. It’s a dark, ice-rich object that currently shines at magnitude 7, putting it within easy range of 35mm and larger binoculars. Whether binoculars or telescope, Ceres is too far away to look like anything more than one of the sky’s many fainter stars.

This mosaic of Cerealia Facula inside Ceres’ Occator Crater combines images obtained from altitudes as low as 22 miles (35 km) above Ceres’ surface. It’s overlain on a topography model gleaned by the Dawn spacecraft so we can see elevations. Elevations are to scale — not exaggerated. The white areas are mostly sodium carbonate salt left after the water / ice they were dissolved in vaporized. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

By good fortune, the dwarf planet just passed its opposition on May 26 and is now closest to the Earth for the year. It’s also easy to find thanks to Jupiter which shines a fist-and-a-half (15°) to the lower left of Ceres. To find this pinprick of light first locate Jupiter, which looks like a brilliant “star” in the southeastern sky around 10:30 p.m. this month. From Jupiter, slide a fist to the right to the bright, orange-red star Antares (an-TAR-eez) in the constellation Scorpius. If you look about 8° (a little less than a fist) to the right and a bit above Antares you’ll see a vertical row of three bright, equally spaced stars. That’s the head of the scorpion.

Italian astronomer and priest Giuseppi Piazzi discovered Ceres on Jan. 1, 1801. He observed it on four separate nights before he was satisfied it was a new discovery.

Point your binoculars at the topmost star of the trio, Graffias. Ceres lies about 3.5° degrees above Graffias. If you place the star in the bottom of your binocular field of view, Ceres will be just above the center. Confirm that it’s the dwarf planet by noting the pattern it makes with the stars near it. The map above shows stars as white-on-black, but if you prefer a more printer-friendly black-stars-on-white version, click here.

Once you’ve found Ceres, you can return the next clear night and make a discovery — it moves! Each night, the dwarf planet slips slowly westward (to the right) following along the arc drawn on the map. I like to make little stick figures connecting Ceres into triangles or squares with other stars in the field of view. When I return the next clear night, its movement will have stretched or bent my mini-constellation out of shape, making it easy to follow.

Wrapped into that stellar point is an amazing world of its own with tens of thousands of craters, some dotted with white, salty spots marking the locations of ancient briny-water seeps from below the crust. The dwarf planet is rich in clay and has a rocky core and ice-rich mantle. Ceres spins once every 9 hours and takes 4.5 years to go around the sun.

Much of what we know about Ceres comes through the eyes and instruments of NASA’s Dawn spacecraft which orbited the little orb between 2015 and 2018. Check out this wonderful album of photos taken during the mission.

I hope you get to see this interesting object with your own eyes while it’s bright and the weather fine.

11 Responses

  1. Good morning! Wonderful post, Bob! I dislike the term dwarf planet, though. I prefer either planetoid or planetismal. And is it right to say there’s only 5, or better yet only 5 named similar objects?

  2. caralex

    I notice you didn’t mention Pallas, Juno and Vesta in your list of ‘dwarf planets’. Have they been demoted? I think Vesta is sometimes also visible to the naked eye in ideal conditions.

  3. Thanks for the info Bob! Ilive in Zanzibar, Tanzania. I think i have got Ceres but will check tomorrow her movement. Jupiter and the four Galillean at one side also a nice setting. Earlier the Moon next to very small Mars. Amazing.

    1. astrobob

      Hi Martijn,
      You’re a long way from where I live! Thanks for sharing your observation with us, and I’m very happy you found Ceres. You’ll know for sure in a night or two. Clear skies!

  4. Martijn Blok

    Hi Bob, Now a am sure I found it. It took me some days and time to get acquainted with nearby stars and patterns. From here you see an arc of little stars and it moves just above it to the west in direction of Graffias. Amazing to realise this little world is part of our solar system. Cheers

    1. astrobob

      Hi Martijn,
      Very happy you found it. It’s always a good reality check to hear from another observer. Ceres may be easy for me but for others it can take a couple nights to get familiar. Thanks for sharing your observation.

  5. kevan hubbard

    I was hoping to spot Ceres and add to Pallas as astroids I’d spied in 2019 but we’re having the wettest June on record,solid gray and interspersed with rain for about 6 days now.looks like nimbostratus hardly in the exotic league of noccullient and nacrous clouds!my Ceres viewing window will soon close, it’s very low as it is.i was hoping to get it added to the list of things I’d seen in my Zeiss 5×10 miniquick monocular as I reckon it’s just within it’s grasp.i can’t remember if I got Pallas in it and I think it was an 8×25 monocular I saw that in no problem.

    1. astrobob

      Kevan,
      I can appreciate those long wet spells. Sometimes they drive me crazy. I hope it clears soon.

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