Changing Planet

Watch Historic Meeting of Two Monster Asteroids in the Sky This Weekend

This mosaic synthesizes some of the best views the Dawn spacecraft had of the giant asteroid Vesta. Dawn studied Vesta from July 2011 to September 2012. This week sky-watchers get to view this giant and its cousin asteroid, Ceres. Courtesy of NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

Ceres and Vesta—two of the biggest and brightest asteroids in the solar system—offer sky-watchers a record-breaking rendezvous as a treat over the holiday weekend.

Not since their discovery more than 200 years ago has anyone observed these two giants of the main asteroid belt pair up so closely in the heavens.

Since spring, keen-eyed sky-watchers using nothing more than binoculars or small telescopes have followed the cosmic duo. The two asteroids have flown in tandem, looping across the Virgo constellation now visible in the southwestern evening skies.

While they are beginning to fade (Ceres shines at magnitude 8.5 and Vesta at magnitude 7.2), the best part of the celestial show happens on the evenings of July 4 and 5, when the pair reach their closest moments. Overnight, the two asteroids will appear separated by only ten arc-minutes, equal to one-third of the width of the moon’s disk.

This simulated orbital view of the solar system shows the relative positions of asteroids Vesta and Ceres in relation to the sun,  Earth and other planets on July 4, 2014. Credit: SkySafari
This simulated orbital view of the solar system shows the relative positions of asteroids Vesta and Ceres in relation to the sun, Earth and other planets on July 4, 2014. Credit: SkySafari

There is no need to fret about any collision between them, however. Their proximity in the sky is simply an illusion, created by their positions relative to each other and to Earth. In reality, some 46 million miles (74 million kilometers) of space will separate the two asteroids.

While Ceres, at 585 miles (940 kilometers) wide is nearly two times larger than Vesta, it appears fainter to us because it is farther away and has a much darker surface.

After July 5, the two will start to drift apart; however, they will remain within 5 degrees of each other (within a binocular’s field of view) until July 11.

See for Yourself

Start your asteroid hunt with the bright beacons of Mars and Spica. They will help point the way to the much fainter field of stars right above them where your targets lie.

Also helping to make it easy, the faint naked-eye star, Zeta Virginis, will be only 1.5 degrees northeast of the asteroids.

This wide-scale skychart shows the the position of asteroids Vesta and Ceres in the constellation Virgo on July 6, 2014. Credit: SkySafari
This wide-scale sky chart shows the position of asteroids Vesta and Ceres in the constellation Virgo on July 6, 2014. Credit: SkySafari offers a detailed finder’s chart and a tip to help you confirm you have bagged Ceres and Vesta: Sketch the positions of a handful of stars around what you suspect are the asteroids through the telescope. Look again in the same field of stars the next night or two. The two that have moved are the asteroids.

And while you are looking at these two giant space rocks, ponder the spacecraft nearby in the same field of view. NASA’s Dawn mission first visited and mapped Vesta in unprecedented detail in 2011 and 2012. It is now on its way to a historic encounter with Ceres in March 2015.

If you end up clouded out or don’t have binoculars to catch this unique sky show, then will be broadcasting the historic asteroid encounter live online from their observatory in the Canary Islands off the coast of West Africa. The webcast begins on July 3 at 8:00 p.m. EDT (00:00 UTC).

Follow Andrew Fazekas, the Night Sky Guy, on Twitter and Facebook.

Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.
  • Dwayne LaGrou

    I was just wondering if they were able to measure the strength of gravity for either of these two asteroids in comparison to the moons and Earths gravity. And we’re they able to tell what the general make up of them is. Rocky or Metallic?
    Thank You, DL

  • Ima Ryma

    I am Dawn, a space probe Earth sent
    To study the asteroid belt,
    Where two woulda been planets went,
    Vesta and Ceres always felt.
    Two thousand eleven I got
    To Vesta, shouting no hello.
    Orbited round and snooped a lot,
    Fourteen months and ’twas time to go,
    On to Ceres. If all goes well,
    I’ll be the first to beat the odds
    Doing double duty – do tell!
    First time orbit – two E.T. bods.

    It’s been a trip to go and find
    Two close encounters of ‘roids kind.

  • philip coleman

    Very Interesting!

  • Dave Mitsky

    I did some observing from the Astronomical Society of Harrisburg’s Naylor Observatory on the night of Saturday, July 5th. Seeing 1 Ceres and 4 Vesta in the same field of view through a 14″ Meade LX200GPS SCT and a 25mm University Optics MK-70 eyepiece (89x) was a real treat!

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