Asteroid Underdog Pallas Bright And Close This Month – Here’s How To See It

Pictures of Pallas (right) taken by the Hubble Space Telescope and a model of its surface. The darker, circled area may be a large impact crater. Pallas is named for Pallas Athena, an alternate name for the Greek goddess Athena of wisdom and courage. Credit: NASA / JPL

Being number two isn’t all that bad. Less pressure than the number one spot and yet you still have a foot in the limelight. Asteroid 2 Pallas was the second asteroid discovered back in the days when asteroids were so few and novel they were called planets. German astronomer Heinrich Olbers accidentally ran across it while attempting to find another asteroid, Ceres, on March 28, 1802.

This week you can see Pallas at its brightest in two decades as it treks from Sextans into Hydra the Water Snake during convenient evening viewing hours. With the asteroid shining at around magnitude 7 – just one level fainter than naked eye visibility – all you need is a pair of binoculars, a map and a clear night.

The path of asteroid 2 Pallas as it slides along the back of the water snake constellation Hydra. It will appear as a star in telescopes and binoculars moving slowly to the north night by night. Stars shown to magnitude 8. Click for large version. Stellarium

At 338 miles across, Pallas bests Vesta in size by just 12 miles, making it the second largest asteroid after Ceres, the only main belt asteroid also classified as a dwarf planet. Unlike the planets, Pallas orbits the sun in a highly inclined orbit (34.8 degrees) taking 4.6 years to complete one spin around the sun. Pallas’ average distance from the sun is 257 million miles, but this month it’s lined up favorably with Earth and only about 115 million miles away. It was last this bright in 1991 and won’t be again until 2028.

Use this wide-field map to help you find Hydra and Alphard, its brightest star at 2nd magnitude. Alphard is roughly one “fist” held at arm’s length below and on either side of Procyon and Regulus. The map shows the sky facing south-southeast around 9 p.m. local time in early March. Stellarium

Being so much smaller than any of the eight planets, Pallas looks exactly like a star through most telescopes. Even the orbiting Hubble Space Telescope, located far above the blurring effects of Earth’s turbulent atmosphere, sees the asteroid as a pixelated object the shape of a flattened sphere with a large, darker “depression” that might be a crater.

The orbit of Pallas is rather wildly inclined, well outside the tilts of the other planets which lie in nearly the same plane. This view shows where Pallas is today March 3, 2014. Credit: NASA/JPL

Don’t expect a mission to the #2 anytime soon; Pallas’ highly tilted orbit makes it extremely difficult, energy and time-wise, to dispatch a probe for in-depth study and photo-taking.

Beautiful slice of the CR2 meteorite NWA 7837 from the Sahara Desert. Pallas’ surface shows similarities with this space rock. Credit: Sergey Vassiliev

That hasn’t stopped astronomers from eking out what they can across the millions of miles that separate us. Pallas receives light from the sun, absorbing some and reflecting the rest back into space. Rocks absorb light according to their internal makeup, imprinting their mineral signatures in the light they reflect back into space. Different rocks, different imprints.

Examining Pallas’ light with a spectrograph, which can dissect light like a doctor working a scalpel, we can identify basic minerals on the asteroid’s surface. From these observations, astronomers have learned that Pallas has much in common with the CR group of carbonaceous chondrite meteorites, both of which are very ancient and contain water and carbon.

This week Pallas will be near Alphard, an orange-tinted star and the brightest in Hydra, making it easy to find. It rides high in the southeastern sky around 9 p.m. local time. At magnitude 2 (Big Dipper brightness), Alphard stands out in a rather empty region of sky. You can find it by reaching your balled fist to Regulus in Leo and looking a little more than a fist below and to its right. Or you can do the same with Procyon in Canis Minor and look below and left.

Next, focus your binoculars on Alphard and use the map to stepping-stone your way to Pallas. The fun begins when you observe the asteroid for a second or third time and watch it move among the stars pulled by the gentle tug of the sun’s gravity.

8 Responses

  1. Troy

    Thanks for the reminder, I forgot this was coming up. It is actually possible the DAWN spacecraft may do a flyby (situated when Pallas crosses the ecliptic plane) as part of an extended mission after it is done with Ceres. I suspect it won’t happen though, for one thing I think Ceres will be much more interesting than most imagine, so they’ll probably try to get into a closer orbit making an extended mission impossible. If it was left to me I’d do the Pallas flyby and send another mission for a Ceres orbiter-rover combination.

    1. astrobob

      Thanks Troy – I thought the possible Dawn flyby was canceled because of a problem with the probe’s reactor wheels. You’re right though that if a flyby were attempted, it would be a “quickie” as the two met in the ecliptic plane.

      1. Troy

        You’re right the reactor wheel as well a generally aging spacecraft is going to give anyone considering an extended mission pause. If it is going to happen I guess it would be at the opposite node in about 840 days, plenty of time to get over there. I don’t think an Eros type landing of the NEAR craft is possible, Ceres is going to have more gravity, maybe you can correct me on that if I’m wrong. In the mean time to quote one of your earlier articles we have to “be our own space ship”

        1. astrobob

          After the Ceres mission is complete I’m not sure what NASA plans to do with the Dawn probe. As you imply, it’s not made for landing given Ceres’ gravity. It might depend on funding whether they just let it orbit or crash it while taking the damn best close-up photos ever on the way down.

          1. Troy

            I found it and photographed it. Let’s just say it is not photogenic, but I’m trying to photograph the first 10 asteroids for a project I’m working on.
            I’d be impressed with anyone who can spot it with binoculars (at least at my observing site and the less than optimal conditions I had), it is pretty dim especially considering it was the second discovered and at its prime right now.
            I looked up Pallas on Wikipedia and found what you had said about the reaction wheel causing the cancellation of the DAWN flyby of Pallas, though no reference listed for it, which I would very much like to see. Since they now use more fuel to take over for the defunct reaction wheel it does seem to be an issue. Checking the Dawn journal I see certain red flags like “the [Ceres] mission will conclude when the hydrazine is exhausted.”

  2. Troy

    I’m writing what will essentially be a 3rd person planetarium program. In addition to the top 10 asteroids I’m going to photograph all the stars 3rd magnitude and brighter. Rather than use the images directly, they will be used as texture maps for their exaggerated stellar counterpart in the display. While it will be stylized with an artistic emphasis rather than an emphasis on accuracy, the actual math behind the scenes is accurate to about an arc minute. All I have at this point is the computational functions for the planets and asteroids. I hope to start my systematic star photography this spring. Yes the nights are longer right now but it has been so darn cold.

    1. astrobob

      Very interesting. I’ve never heard of someone doing this. Have to ask – why not use one the many planetarium programs already out there?

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