Triple Planetary Alignment

Most people think that astronomy can only be done with big expensive telescopes from remote locations far from city lights. But there’s another side to astronomy that can be appreciated everywhere using nothing more the your naked eyes.

A superb opportunity to enjoy this second type of astronomy occurs during the last two weeks of May and extends into early June. During this period, three of the five naked-eye planets will all converge in the evening sky in what is referred to as a triple planetary alignment. At the climax of this celestial grouping, the brilliant planets Jupiter and Venus will be joined by fainter Mercury to form a tight nearly equilateral triangle.

On May 26, 2013, Jupiter, Venus and Mercury will form a conspicuous triangle low in the north western sky during evening twilight. For views of this planetary alignment on other days, see: 2013 Triple Planetary Alignment Viewing Charts.

On May 26, 2013, Jupiter, Venus and Mercury will form a conspicuous triangle low in the north western sky during evening twilight. For views of this planetary alignment on other days, see: 2013 Triple Planetary Alignment Viewing Charts.

During the alignment, the distances of the three planets from Earth are quite different from each other. Jupiter is 564 million miles from us while Venus is about 1/4 the distance at 152 million miles. Mercury is closer still at just 105 million miles.

So how exactly is this alignment possible? The orbits of the planets all lie nearly in the same plane around the Sun. If we imagine we are high above the Solar System and look down, it would resemble the figure below with the planets orbiting the Sun in the counter-clockwise direction (as indicated by the yellow arrows).

The position of the plants as seen from above the Solar System during the great triple planetary alignment of 2013.

The position of the plants as seen from above the Solar System during the great triple planetary alignment of 2013.

If you draw a straight line from Earth to each of the three planets, you’ll see that they all lie in nearly the same direction. That’s why Jupiter, Venus and Mercury line up so closely during the planetary grouping. Notice also that all three planets lie on the opposite side of the Sun from Earth. Although Mars is also shown, it’s nearly in the same direction as the Sun and is slowly emerging from the solar glare into the morning sky. This diagram shows the planetary positions on May 26 but the period leading up to that date is well worth watching.

If you face to the northwest about 40 minutes after sunset on May 18, you will immediately notice two very bright “stars”. The upper one is Jupiter while the brighter one to the lower right is Venus. If you have a low horizon with no trees, buildings or mountains blocking your view, you may also catch a brief glimpse Mercury (lower right of Venus) very low on the horizon. Don’t worry if you can’t see Mercury yet. Both Venus and Mercury appear higher each night as the distance between them shrinks. On the other hand, Jupiter appears lower each evening, assuming you look at the same time each night. The net result is that all three planets slowly converge over the course of the next ten days.

The pinnacle of this celestial ballet occurs on the evening of May 26 when all three planets lie within 3° of each other. You’ll be able to hide them behind a quarter (large U.S. coin) when held at arms length. After May 26, Jupiter continues to drop in the sky while Venus and Mercury rise. Since they move at different rates, the planets slowly spread appart.
Mercury climbs fastest out of twilight’s glow but the quick planet’s race ends on June 12 when it reaches greatest eastern elongation (this doesn’t happen for Venus until November 1). After that, Mercury begins to descend back into twilight. It passes within 2° of Venus on June 20. Mercury completely disappears into the solar glare by the end of June; Jupiter suffers a similar fate two weeks earlier.

A computer simulation illustrates the appearance of the 2013 Triple Planetary Alignment on 3 evenings in late May. Visit 2013 Triple Planetary Alignment Viewing Charts to see individual charts for every day from May 18 through June 8.

A computer simulation illustrates the appearance of the 2013 Triple Planetary Alignment on three evenings in late May. Visit 2013 Triple Planetary Alignment Viewing Charts to see individual charts for every day from May 18 through June 8.

The changing appearance of the planetary grouping can be seen in a series of computer generated diagrams for every evening from May 18 through June 8 (see: 2013 Triple Planetary Alignment Viewing Charts).

Triple planetary alignments take place every year or two, but many occur too close to the Sun where they remain hidden from view. In other instances, the alignment occurs when one or more of the planets is rather faint. The 2013 alignment is especially favorable because it’s easy visibility in the evening sky with three bright planets. So don’t miss this rare and beautiful planetary alignment.

Fred Espenak

Note: The close alignment of Jupiter, Venus and Mercury is sometimes called a conjunction, but this is incorrect. Technically, a conjunction occurs when two (or more) astronomical bodies share the same celestial longitude.

Update: See photos of the 2013 Triple Planetary Alignment.

Near-Earth Asteroid 2012 DA14

A few months ago, I blogged about the minor planet Toutatis which passed within 4.3 million miles (6.9 million kilometers) of Earth on December 12, 2012. This is about 18 times the distance to the Moon, and is considered a close approach relative to the scale of the Solar System. But this pales in comparison to a minor planet called 2012 DA14, which was discovered last year (February 23, 2012), just seven days after passing 1.6 million miles (2.6 million km) from Earth.

The near-Earth asteroid 2012 DA14 passed 17,200 miles (27,700 km) from the surface of Earth on February 15, 2013. Six hours after its closest approach, 2012 DA14 was imaged from Bifrost Astronomical Observatory. Photo copyright 2013 by Fred Espenak.

The near-Earth asteroid 2012 DA14 passed 17,200 miles (27,700 km) from the surface of Earth on February 15, 2013. Six hours after its closest approach, 2012 DA14 was imaged from Bifrost Astronomical Observatory. Photo copyright 2013 by Fred Espenak.

With a diameter of about 50 meters (160 ft), 2012 DA14 is truly a near-Earth asteroid. This year’s flyby (February 15, 2013) brought the asteroid even closer as it passed 17,200 miles (27,700 km) from the surface of Earth. This is well inside the orbits of geosynchronous satellites which travel at distances of about 22,200 miles (35,800 km) from Earth’s surface.

At its closest, 2012 DA14 was above the Eastern Hemisphere and not visible from the USA. About 7 hours later, the asteroid was above the horizon in Arizona, and I was able to image it from Bifrost Observatory. By that time (03:30 UT on Feb 16), 2012 DA14 was quickly receding from Earth at a distance of 120,300 miles (193,700 km). It was now 100x fainter at magnitude 12.3 (compared to magnitude 7.4 at nearest approach).

Nevertheless, 2012 DA14 was still moving rapidly across the sky making it a challenge to image. Even in the short 15 second exposures I used, the asteroid left long trails. Below is a time-lapse animation made from a series of images acquired with a 12″ ASA astrograph.

Time-Lapse of Near-Earth Asteroid 2012 DA14 from Fred Espenak on Vimeo.

This is a record close approach for a known object of any size. Asteroids this large actually hit the Earth about once every 1000 years. The effects of such a direct hit could completely level an unfortunate city in its path, or produce a devastating tsunami in the case of an ocean hit. Astronomers have only recently received funding to discover and track potentially dangerous asteroids, but most of these objects are faint and hard to detect unless they are already close to Earth. More funding is needed to catalog all near-Earth asteroids as soon as possible.

Sixty-five million years ago, a much larger 10-kilometer size asteroid collided with Earth, resulting in the extinction of 75% or more of all species on Earth including the dinosaurs (see: Chicxulub crater and Cretaceous–Paleogene extinction event). Perhaps someday, we will have all of these threats identified and will have a defense system in place to destroy or deflect such objects. But for the time being, such schemes remain the grist of Hollywood movies, and planet Earth (and mankind) remains at risk.

Fred Espenak

Toutatis

Toutatis

Minor planet Toutatis (4179) is captured in a series of 60-second exposures (with a 60-second gap between exposures) on December 12 shortly before reaching its closest distance to Earth (7 million kilometers). Photo copyright 2012 by Fred Espenak

During the second week of December 2012, the minor planet Toutatis (4179) made a close approach to Earth passing within 7 million kilometers (4 million miles (on Dec. 12 at 06:40 UT). This is about 18 times the average Earth-Moon distance which is quite close relative to the scale of the Solar System.

The rapid motion of Toutatis is revealed in a video made from a series of 60-second exposures shot over a 102-minute period on December 13. Photo copyright 2012 by Fred Espenak

Toutatis is an irregular 5-kilometer chunk of rock that makes a close approach to Earth every four years. Its orbit is chaotic because of the large perturbations it undergoes from the gravitational interact with Earth and Jupiter. In fact, Toutatis is in a 3:1 orbital resonance with Jupiter, and a 1:4 orbital resonance with Earth (which is why it passes close to Earth every 4 years).

Toutatis was first sighted in February 1934, but it was then lost. It wasn’t until January 1989 until it was rediscovered by French astronomer Pollas.

According to Minor Planet Circ. 16444: “Named after the Gaulish god, protector of the tribe. This totemic deity is well known because of the cartoon series “Les aventures d’Asterix” by Uderzo and Goscinny. This tells the stories of two almost fearless heroes living in the last village under siege in Roman-occupied Gaul in 50 B.C., and whose only fear is that the sky may fall onto their heads one day. Since this object is the Apollo object with the smallest inclination known, it is a good candidate to fall on our heads one of these days… But as the chief of the village always says: “C’est pas demain la veille…” Citation written by the discoverer and A. Maury and endorsed by J. D. Mulholland, who with Maury obtained the discovery plates.”

I imaged Toutatis on two nights from Bifrost Observatory using the ASA N12 Astrograph. It was quite amazing to see how quickly the minor planet crossed the field of the camera – over 3 degrees per day.

The rapid motion of Toutatis is revealed in a video made from a series of 60-second exposures shot over a 102-minute period on December 13. Photo copyright 2012 by Fred Espenak on Vimeo.

Because of its close proximity to Earth, astronomers of NASA’s Goldstone dish were able to obtain radar images of Toutatis with unprecedented resolution.

According to Michael Busch (NRAO): “Toutatis appears to have a complicated internal structure. Our radar measurements are consistent with the asteroid’s little lobe being ~15% denser than the big lobe; and they indicate 20% to 30% over-dense cores inside the two lobes.” This suggests that Toutatis may be a loose composite of smaller space rocks. “Toutatis could be re-accumulated debris from an asteroid-asteroid collision in the main belt,” says Busch.

Fred Espenak

Radar Image of Toutatis from Goldstone

Radar Image of Toutatis from Goldstone

Jupiter’s 2012 Opposition

TauJup12-02w.jpg

This image is a wide angle view of the sky looking east around 8 pm local time on December 3. Orion has just risen (lower right) and above it is Taurus and the planet Jupiter (near center) shining as a brilliant white star. For complete details about the photo see Taurus & Jupiter – 2. Photo copyright 2012 by Fred Espenak.

Go out any clear evening in December and look east around 7 or 8 pm. You’ll see a dazzlingly bright star which is, in fact, the planet Jupiter. Earlier this week (Dec. 3) the giant planet was at opposition with the Sun. In other words, the Sun and Jupiter were in opposite directions in the sky as seen from Earth. While the Sun is highest in the sky around 12 noon, Jupiter is best seen at 12 midnight. If you could look down on the Solar System from above, you would see that the Sun, Earth and Jupiter are lined up (in that order).

For amateur astronomers, this is the perfect time to observe Jupiter because it is closest to Earth and is visible all night long. Jupiter’s distance is currently 4.07 AU from Earth and 5.05 AU from the Sun. Compare this to Jupiter’s position six months from now when it is in conjunction with the Sun and hidden in the solar glare. It will then be 6.14 AU from Earth and 5.12 AU from the Sun (see: Jupiter 2012 for a complete ephemeris of the planet during the year).

Jupiter is the largest planet in the Solar System and has an equatorial diameter of 143,000 kilometers. This is 11.1 times Earth’s diameter. Even giant Saturn is just 84% the diameter of Jupiter. Of course, if we compare Jupiter to the Sun, it’s diameter is a mere 10% of the Sun’s. At a mean distance over five times greater than Earth’s from the Sun, Jupiter takes 11.86 years to complete one orbit around our star.

Jupiter currently subtends an angle of 48.5 arc-seconds – the largest of the year. Even a modest telescope will reveal Jupiter’s disk, its cloud belts (appearing like pale stripes), and its four biggest moons Io, Europa, Ganymede, and Callisto (appearing like bright stars aligned in the same plane as Jupiter’s cloud belts).

The movie above is time-lapse of Jupiter, taken by NASA’s Voyager 1 spacecraft as it approached the planet in February 1979. It covers a period of 95 hours, and and shows how rapidly Jupiter’s clouds rotate. It also features appearances of three of Jupiter’s innermost moons: Io, Europa and Ganymede. You can also see the shadows of the moons race across Jupiter’s clouds tops.

Although I’ve done a lot of astrophotography, none of it involves close-ups of the planets. However, Damian Peach, an amateur astronomer from southern England is a master of high resolution planetary imaging. You’d be excused if you mistake Peach’s images for something shot by NASA’s Voyager. His images are that good! Take a look at some of Peach’s recent images of Jupiter.

TauJup12-01w

Jupiter reached opposition with the Sun just two hours before this image was made on Dec. 3. Jupiter appears as a brilliant white star above the Hyades star cluster in Taurus. The dipper-shapped Pleiades is to the upper right. For complete details about the photo see Taurus & Jupiter – 1. Photo copyright 2012 by Fred Espenak.

Even without a telescope, the view of Jupiter in Taurus is beautiful. Below Jupiter is the the v-shaped group of stars called the Hyades. The bright orange star in the Hyades is Aldebaran. To the upper right is a tiny dipper-shaped star cluster known as the Pleiades. I’ll have more to say about the Pleiades in a future blog.

Over the course of the next few months, Jupiter will slowly change position against the background stars of Taurus. And just in case you’re wondering, the placement of Jupiter in Taurus has absolutely no significance on the life and affairs of Earth’s inhabitants. Astrology has been around for thousands of years and yet, there is no scientific evidence to support any of its principles, postulates or claims. To put it more colloquially, astrology is a bunch of baloney! Read all about it in Phil Plait’s blog on astrology.

In the meantime, go out tonight and enjoy the view of Jupiter and Taurus.

Fred Espenak