Astro Bob: Planet kings Jupiter and Saturn return at dawn; Apophis flyby this weekend - Duluth News Tribune

Jupiter and Saturn are two of the most beautiful planets to observe with a telescope. Jupiter displays colorful, ever-changing clouds, while Saturn shows off its iconic rings. The Hubble Space Telescope captured these images in 2020. (NASA, ESA, A. Simon (Goddard Space Flight Center), M.H. Wong (University of California, Berkeley), and the OPAL Team)

Because both planetary giants compete with the growing dawn light and lie near the horizon, bring along a pair in binoculars to help you scoop them up. Jupiter will stand just 3° high and Saturn about 6° during a narrow window of visibility that begins about an hour before sunrise and ends 20 minutes later.

Despite its lower altitude Jupiter will be easier to see because it's quite a bit brighter than Saturn. Back in December, the two planets stood just a fraction of a degree apart; now almost 9° separates them or about one fist held horizontally at arm's length.

Jupiter, the closer of the two, orbits the sun more quickly. It passed Saturn in December and has kept on going like a dog loosened from its leash. On October 31, 2040 the giant planet will lap the ring king again though not nearly as closely as it did in 2020. On that distant date, the duo will stand 1.1° apart. I hope we're both around to see it.

If you train a small telescope on Jupiter on the morning of the 5th you'll see its four brightest moons strung out in a line west of the planet. I = Io; II = Europa, III = Ganymede and IV = Callisto. (Stellarium)

You could just wait until later this month to welcome the return of Jupiter and Saturn, when they'll be higher up and easier to see, but Friday morning (March 5) is special. Mercury will nestle very close to Jupiter — just 0.4° away! The smallest and innermost planet shines at magnitude 0 (brighter than Saturn) and should be obvious once you spot Jupiter. At the same time, all four of Jupiter's brightest moons will be splayed out to the right (west) of the planet in a line with Europa closest, followed by Io, Ganymede and Callisto.

The waning crescent moon joins the scene on Wednesday, March 10 as Mercury sinks closer to the horizon. Use binoculars to help you spot this arc of celestial delights. (Stellarium)

Then on Wednesday morning, March 10, the "old" crescent moon enters the scene to the right of Saturn. Mercury may be trickier to see by then, but with clear skies and a good horizon you can start at the moon and use it to "planet-hop" to the others.

After the 5th, Mercury and Jupiter part, while Jupiter and Saturn slowly gain altitude. By month's end, they'll still be relatively low at dawn but considerably easier to see. Both are located in the constellation Capricornus the Sea-goat and will stand high and bright together in the evening sky from August through November.

Mars and the Pleiades star cluster continue to make a pretty sight together this week. To their left is the larger, closer star cluster in the shape of the letter V called the Hyades (HI-uh-deez). This photo was taken on March 2 with a 35mm lens at f/2.8, ISO 4000 and an 8-second exposure. (Bob King)

Meanwhile, Mars continues to catch the eye as it glides beneath the Pleiades star cluster. It's now headed toward the Winter Hexagon, a huge asterism comprised of six of the brightest stars in the winter sky. It crosses into the figure on March 25 and remains there through May as it continues to fade with increasing distance from the Earth. Mars won't be close and brilliant again until the fall of 2022.

Speaking of close, the asteroid 99942 Apophis will be making a relatively close approach to the Earth on Saturday, March 6. You may have heard of Apophis before in the context of "killer asteroids". This approximately 1/4-mile-wide (370 meters) object has a 1 in 380,000 chance of smashing into the Earth during its April 12, 2068 closer flyby. While small, that's significant.

But as often happens with potentially hazardous asteroids (PHAs), further observations refine the object's orbit and more often than not reduce the probability of a potential impact to near zero. Back in December 2004, astronomers were initially concerned when early observations showed that Apophis had a 2.7 percent chance of hitting the Earth or Moon during its April 13, 2029 flyby. Additional observations eliminated that probability.

Astronomers will be monitoring Apophis closely during its pass of Earth this weekend. No worries — the asteroid won't get any closer than 10.4 million miles (16.8 million km) this time around.

At the time this photo was taken on March 2, 2021, Apophis (arrowed) was 10.6 million miles (17 million km) from Earth. The telescope tracked the motion of the asteroid, which makes the stars show as trails. (Gianluca Masi)

A dim object in even a large telescope, you'll still have the opportunity to see it. Italian astrophysicist Gianluca Masi will livestream the flyby starting at 6 p.m. March 5 on his Virtual Telescope website.

Things flying around up there sure have a way of keeping things interesting down here.

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

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https://www.duluthnewstribune.com/astro-bob/6915765-Astro-Bob-Planet-kings-Jupiter-and-Saturn-return-at-dawn-Apophis-flyby-this-weekend

2021-03-04 17:36:00Z
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