The Opposition of Mars

March 28, 2014:  By the time you finish reading this story, you'll be about 1,000 km closer to the planet Mars.

Earth and Mars are converging for a close encounter. As March gives way to April, the distance between the two planets is shrinking by about 300 km every minute.  When the convergence ends in mid-April, the gulf between Earth and Mars will have narrowed to only 92 million km--a small number on the vast scale of the solar system. 

Astronomers call this event an "opposition of Mars" because Mars and the Sun are on opposite sides of the sky.  Mars rises in the east at sunset, and soars almost overhead at midnight, shining burnt-orange almost 10 times brighter than a 1st magnitude star.

Oppositions of Mars happen every 26 months. Of a similar encounter in the 19th century, astronomer Percival Lowell wrote that "[Mars] blazes forth against the dark background of space with a splendor that outshines Sirius and rivals the giant Jupiter himself."

In other words, it's really easy to see.

There are two dates of special significance:

April 8th is the date of opposition, when Mars, Earth, and the sun are arranged in a nearly-straight line. 

If the orbits of Mars and Earth were perfectly circular, April 8th would also be the date of closest approach.  However, planetary orbits are elliptical--that is, slightly egg-shaped--so the actual date of closest approach doesn't come until almost a week later.

Mars, photographed on March 6, 2014, by Australian amateur astronomer Anthony Wesley using a 16-inch telescope. More

On April 14th, Earth and Mars are at their minimum distance: 92 million km, a 6+ month flight for NASA's speediest rockets. You won't have any trouble finding Mars on this night. The full Moon will be gliding by the Red Planet in the constellation Virgo, providing a can't-miss "landmark" in the midnight sky.  

Remarkably, on the same night that Mars is closest to Earth, there will be a total lunar eclipse.  The full Moon of April 14-15 will turn as red as the Red Planet itself.  A video from Science@NASA has the details.

Although these dates are special, any clear night in April is a good time to look at Mars.  It will be easy to see with the unaided eye even from brightly-lit cities.  With a modest backyard telescope, you can view the rusty disk of Mars as well as the planet's evaporating north polar cap, which has been tipped toward the sun since Martian summer began in February. Experienced astro-photographers using state-of-the-art digital cameras can tease out even more—for example, dust storms, orographic clouds over Martian volcanoes, and icy fogs in the great Hellas impact basin. The view has been described by some observers as "Hubblesque."

Update:  You're now 1000 km closer to Mars.

Credits:

Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit: Science@NASA

More information:

The distances and velocities cited in this story were calculated by JPL's online HORIZONS ephemeris.  All velocities are correct for March 31, 2014.

Oppositions of Mars happen every 26 months. The racetrack model of planetary orbits explains why.  Earth and Mars are like runners on a track. Earth is on the inside, Mars is on the outside.  Every 26 months, speedy Earth catches up to slower Mars and laps it.  Opposition occurs just as Earth takes the lead.

Because planetary orbits are elliptical, not all oppositions are the same.  In 2003, Mars made its closest approach to Earth in 50,000 years, an apparition that mesmerized sky watchers all over the world.  The 2014 opposition of Mars is a much more "run-of-the-mill" opposition--not historic, but beautiful nonetheless.

Source: NASA

Has This New Discovery By Astronomers Confirmed there is a 'Planet X'?

Astronomers have extended the range of our Solar System with the discovery of a new 'dwarf planet' orbiting our Sun. The planet, currently technically labeled '2012 VP113', has an elliptical orbit that brings it to within 80AU of the Sun (an 'AU' is the unit of distance from the Sun to Earth) at perihelion (closest point in its orbit to the Sun) - some three times the distance from the Sun to Neptune - while it gets as far as 450AU away at the other end of its orbit. The object is not unique: astronomers have previously discovered another similar dwarf planet, named 'Sedna'. Indeed, the new discovery, by astronomers Scott Sheppard and Chad Trujillo, hints that there are a multitude of dwarf planets orbiting the Sun in a location known as the 'inner Oort cloud'.

An intriguing coincidence is that the current positions of both Sedna and 2012 VP113 - which are also near both their perihelions - are very similar, leading to some speculation of an unknown, massive body orbiting our Sun well beyond our current sensing abilities - a 'Planet X':

The latest work has already thrown up an intriguing possibility. The angle of the body's orbit and that of Sedna's are strikingly similar, an effect most likely caused by the gravitational tug of another, unseen body. One possibility is a "Super Earth" that traces so large an orbit around the sun that it has never been seen.

"If you took a Super Earth and put it a few hundred astronomical units out, the gravity could shepherd Sedna and this new object into the orbits they have," said Sheppard.

Over at her Planetary Society blog, Emily Lakdawalla has a more detailed breakdown of the discovery, the coincidences, and what it might mean for the Planet X theory. She notes that for a an object of that size to form ('accrete'), it needs to be in a circular orbit - so the elliptical orbit of these two dwarf planets suggests that they were 'scattered' by something at some point after they formed. But the 'Planet X' theory isn't the only possible explanation - the planets may have been thrown into their current orbits by a star that passed within "several hundred AU of the Sun and disturbed orbits of objects it passed near", or it may be due to the fact that Earth was born in a star cluster.

It's really quite striking how close Sedna and 2012 VP113 are to each other right now, both close to their perihelia, both at around 80 AU.Here's an illustration that I put together using the JPL Small-Body Database Browser that shows you just how close they are.

Their current proximity is mostly a coincidence, given the fact that they have different orbital periods; there's nothing about their orbits that says they should be in the same place at the same time, except for the fact that their orbits happen to take them to similar spots in the sky when they are close to the Sun. But we are more likely to discover such objects when they are near perihelion (hence brighter and moving faster), so given the proximity of their perihelia they would've been somewhat close to each other in the sky because that's where we could see them both.

The fact that they have perihelia at similar locations is an interesting observation, though. And it's one that Trujillo and Sheppard noticed, too... They went on to hypothesize that the clustering of argument of perihelia resulted from "a massive outer Solar System perturber" [and] showed that it works for a super-Earth at 250 AU, but "This configuration is not unique and there are many possibilities for such an unseen perturber."

...I have confess to a bias here: I really wanted this coincidence in argument of perihelion to be strong evidence of a planet X. I would love for there to be a planet X. So would Trujillo and Sheppard, evidently, because they spent quite a bit of space showing it could work. And so would Nature, because then the first clear indication of a planet X would be in an article published in their journal.

But Hal [planetary scientist Hal Levison] dashed my hopes, or at least my certainty. "It's a very weak result," he told me; and indeed the paper spends more column inches on what 2012 VP113 tells us about the inner Oort cloud as a population than it does about this potential "perturber."

"There may be other explanations for this, rather than the extreme position of, "it's a planet"; but I can believe there's something going on".

In other words: something threw these planets into their elliptical orbits, but we still don't know what. Watch this...errr...space.

Link: A second Sedna! What does it mean?

Source: Daily Grail