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NASA Jet Propulsion Laboratory via YouTube
NASA Jet Propulsion Laboratory via YouTube

The Juno Mission: NASA Celebrates Independence Day by Invading Jupiter

NASA Jet Propulsion Laboratory via YouTube
NASA Jet Propulsion Laboratory via YouTube

With planetary invasions being an Independence Day tradition, it's fitting that NASA's Juno spacecraft will enter Jupiter's orbit today, July 4, after a five-year journey to the outer solar system. Juno is the robot equivalent of Indiana Jones: a celestial archaeologist on an expedition to find Jupiter's core—and, hopefully, solve the mystery of the solar system's origin. 

HOW IT ENTERS JUPITER'S ORBIT

Juno's insertion into Jupiter's orbit will begin at 8:18 p.m. PDT on July 4, 2016. This involves a 35-minute "burn," during which time the spacecraft reorients itself and the British-built Leros 1b engine fires up so as to slow Juno's speed. (Juno will be traveling 165,000 mph on arrival.) The burn is crucial, and a failure would mean that the spacecraft zips past Jupiter and into the void. Success, however, means Juno is sufficiently slowed to be captured by Jupiter's gravity and thus enters orbit.

Juno does all of this in autopilot, the final commands having been issued by humans on June 30 and blasted to the spacecraft using NASA's Deep Space Network. During orbital insertion, the spacecraft's science instruments and all unnecessary computer features are disabled. (More features increase the likelihood of computer crashes.) Jupiter's intense radiation environment is notoriously hard on spacecraft computers, and in the event that Juno's computer is zapped by a high-energy particle, it is designed to immediately reset and resume the burn. Scientists, meanwhile, will wait anxiously for Juno to send a message to the Deep Space Network that has been compared to the "emergency broadcast signal" on television and radio. A certain tone will mean the spacecraft has achieved a successful orbital insertion.

Juno's unique design—three colossal solar panels affixed to an 11.5-ft. spacecraft at the center—is dictated by the low levels of sunlight available in the outer solar system. The sun appears 1/25 as bright at Jupiter as at Earth. The spacecraft will remain oriented to collect as many photons as possible from the Sun, and will spin like a top, twice per minute in order to maintain stability and to allow each instrument on Juno's scientific payload to collect data from Jupiter.

HOW JUNO'S INSTRUMENTS WILL STUDY JUPITER

Screengrab from NASA fact sheet. Image credit: NASA

Juno's science instruments—all but one built into the core part of the triple-bladed spacecraft—will each collect certain types of data for scientists to analyze back on Earth. The Gravity Science instrument will map the distribution of Jupiter's interior mass, and thus its gravity. The Magnetometer will meanwhile study Jupiter's magnetic field and its massive and mystifying polar magnetosphere. It will also examine Jupiter's interior dynamics. The Microwave Radiometer [PDF] will the study water content of Jupiter's deep atmosphere so as to reveal the oxygen content of Jupiter. An Ultraviolet Imaging Spectrograph and the Jovian Infrared Auroral Mapper will study Jupiter's atmosphere and auroras, while the JunoCam will take high-resolution photographs of Jupiter and its terrifying and beautiful atmosphere. (It has already returned images.)

But that's not all. The Radio and Plasma Wave Sensor and the Jovian Auroral Distribution Experiment will characterize the nature of the magnetic field and atmosphere, and auroras in particular. Lastly, the Jovian Energetic Particle Detector Instrument—JEDI—also concerns itself with Jupiter's magnetosphere, focusing on the "energy and distribution of ions, particularly hydrogen, helium, oxygen and sulphur, to see if there is any change over time." (What better than a Jedi to study energy that surrounds, penetrates, and binds?)

WHAT DON'T WE KNOW ABOUT JUPITER?

A lot. Thanks to the Galileo mission that ended in 2003, we do know much more about Jupiter and its system of moons than we did before. Among many other things, planetary scientists using Galileo data discovered giant thunderstorms along Jupiter's turbulent equator, complete with lightning strikes one thousand times more powerful than those found on Earth [PDF]. Cloudless "dry" spots of low humidity were discovered by a probe dropped into Jupiter, to its doom. The origin of the planet's rings were also worked out: They were formed from the debris left behind after meteoroid collisions with Jupiter's moons.

And yet for all we've learned, Jupiter remains a giant, terrifying mystery. Enter Juno, named after the wife of Jupiter in Roman mythology. Among the goddess's powers: the ability to see through clouds. And that power is in great demand at Jupiter, the largest known planet in the solar system. No one is completely certain what comprises Jupiter, and its oxygen content remains a mystery. Oxygen percentages might seem like snooze-level science geekery, but the answer to that question, according to NASA, is "the most important missing piece in our understanding of how our solar system formed." Moreover, it remains a mystery whether Jupiter is gas all the way down, or whether there a giant metal Earth-sized planet at its center. (Cybertron?) Just how far down do Jupiter's famous brown and tan cloud bands of clouds go? What's causing Jupiter's spectacular auroras? Juno will help us to answer these questions.

Hubble captures vivid auroras in Jupiter's atmosphere in June 2016. Image credit: Hubblesite.org

FROM DEORBITING TO DISINTEGRATION

Juno will orbit a path along Jupiter's poles [PDF], which NASA describes as "best for mapping and monitoring a planet" and the same type of orbit used by many of Earth's satellites. This means that Juno will be the first spacecraft to get a good look at Jupiter's poles. Each orbit around Jupiter will take 11 days. Because a Jupiter day is only 10 hours long, this means that Juno will have mapped and studied the entire planet in 33 orbits. These orbits will get perilously close to the tops of Jupiter's clouds—a distance of 3100 miles. NASA notes that if Jupiter were a basketball, Juno would be flying one-third of an inch from the ball's surface. 

In October 2017, the spacecraft's mission will end and it will be "deorbited," plunging beneath Jupiter's clouds, where it will ultimately disintegrate. While this might seem like an ignominious end, it is, in fact, a heroic one. By sacrificing itself in the unforgiving hell that is the interior of Jupiter, Juno spares the surrounding moons of the Jovian system the risk of Earthly contamination. Europa, to name one such moon, is thought to harbor life. When the Europa missions get underway, we will know for sure that the life discovered is not of terrestrial origin. 

You can follow the Juno mission on NASA TV or on NASA's Eyes on the Solar System application. 

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Look Up! Residents of Maine and Michigan Might Catch a Glimpse of the Northern Lights Tonight
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iStock

The aurora borealis, a celestial show usually reserved for spectators near the arctic circle, could potentially appear over parts of the continental U.S. on the night of February 15. As Newsweek reports, a solar storm is on track to illuminate the skies above Maine and Michigan.

The Northern Lights (and the Southern Lights) are caused by electrons from the sun colliding with gases in the Earth’s atmosphere. The solar particles transfer some of their energy to oxygen and nitrogen molecules on contact, and as these excited molecules settle back to their normal states they release light particles. The results are glowing waves of blue, green, purple, and pink light creating a spectacle for viewers on Earth.

The more solar particles pelt the atmosphere, the more vivid these lights become. Following a moderate solar flare that burst from the sun on Monday, the NOAA Space Weather Prediction Center forecast a solar light show for tonight. While the Northern Lights are most visible from higher latitudes where the planet’s magnetic field is strongest, northern states are occasionally treated to a view. This is because the magnetic North Pole is closer to the U.S. than the geographic North Pole.

This Thursday night into Friday morning is expected to be one of those occasions. To catch a glimpse of the phenomena from your backyard, wait for the sun to go down and look toward the sky. People living in places with little cloud cover and light pollution will have the best chance of spotting it.

[h/t Newsweek]

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Kevin Gill, Flickr // CC BY-2.0
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10 Facts About the Dwarf Planet Haumea
Kevin Gill, Flickr // CC BY-2.0
Kevin Gill, Flickr // CC BY-2.0

In terms of sheer weirdness, few objects in the solar system can compete with the dwarf planet Haumea. It has a strange shape, unusual brightness, two moons, and a wild rotation. Its unique features, however, can tell astronomers a lot about the formation of the solar system and the chaotic early years that characterized it. Here are a few things you need to know about Haumea, the tiny world beyond Neptune.

1. THREE HAUMEAS COULD FIT SIDE BY SIDE IN EARTH.

Haumea is a trans-Neptunian object; its orbit, in other words, is beyond that of the farthest ice giant in the solar system. Its discovery was reported to the International Astronomical Union in 2005, and its status as a dwarf planet—the fifth, after Ceres, Eris, Makemake, and Pluto—was made official three years later. Dwarf planets have the mass of a planet and have achieved hydrostatic equilibrium (i.e., they're round), but have not "cleared their neighborhoods" (meaning their gravity is not dominant in their orbit). Haumea is notable for the large amount of water ice on its surface, and for its size: Only Pluto and Eris are larger in the trans-Neptunian region, and Pluto only slightly, with a 1475-mile diameter versus Haumea's 1442-mile diameter. That means three Haumeas could fit sit by side in Earth—and yet it only has 1/1400th of the mass of our planet.

2. HAUMEA'S DISCOVERY WAS CONTROVERSIAL.

There is some disagreement over who discovered Haumea. A team of astronomers at the Sierra Nevada Observatory in Spain first reported its discovery to the Minor Planet Center of the International Astronomical Union on July 27, 2005. A team led by Mike Brown from the Palomar Observatory in California had discovered the object earlier, but had not reported their results, waiting to develop the science and present it at a conference. They later discovered that their files had been accessed by the Spanish team the night before the announcement was made. The Spanish team says that, yes, they did run across those files, having found them in a Google search before making their report to the Minor Planet Center, but that it was happenstance—the result of due diligence to make sure the object had never been reported. In the end, the IAU gave credit for the discovery to the Spanish team—but used the name proposed by the Caltech team.

3. IT'S NAMED FOR A HAWAIIAN GODDESS.

In Hawaiian mythology, Haumea is the goddess of fertility and childbirth. The name was proposed by the astronomers at Caltech to honor the place where Haumea's moon was discovered: the Keck Observatory on Mauna Kea, Hawaii. Its moons—Hi'iaka and Namaka—are named for two of Haumea's children.

4. HAUMEA HAS RINGS—AND THAT'S STRANGE.

Haumea is the farthest known object in the solar system to possess a ring system. This discovery was recently published in the journal Nature. But why does it have rings? And how? "It is not entirely clear to us yet," says lead author Jose-Luis Ortiz, a researcher at the Institute of Astrophysics of Andalusia and leader of the Spanish team of astronomers who discovered Haumea.

5. HAUMEA'S SURFACE IS EXTREMELY BRIGHT.

In addition to being extremely fast, oddly shaped, and ringed, Haumea is very bright. This brightness is a result of the dwarf planet's composition. On the inside, it's rocky. On the outside, it is covered by a thin film of crystalline water ice [PDF]—the same kind of ice that's in your freezer. That gives Haumea a high albedo, or reflectiveness. It's about as bright as a snow-covered frozen lake on a sunny day.

6. HAUMEA HAS ONE OF THE SHORTEST DAYS IN THE ENTIRE SOLAR SYSTEM.

If you lived to be a year old on Haumea, you would be 284 years old back on Earth. And if you think a Haumean year is unusual, that's nothing next to the length of a Haumean day. It takes 3.9 hours for Haumea to make a full rotation, which means it has by far the fastest spin, and thus shortest day, of any object in the solar system larger than 62 miles.

7. HAUMEA'S HIGH SPEED SQUISHES IT INTO A SHAPE LIKE A RUGBY BALL.

haumea rotation gif
Stephanie Hoover, Wikipedia // Public Domain

As a result of this tornadic rotation, Haumea has an odd shape; its speed compresses it so much that rather than taking a spherical, soccer ball shape, it is flattened and elongated into looking something like a rugby ball.

8. HIGH-SPEED COLLISIONS MAY EXPLAIN HAUMEA'S TWO MOONS.

Ortiz says there are several mechanisms that can have led to rings around the dwarf planet: "One of our favorite scenarios has to do with collisions on Haumea, which can release material from the surface and send it to orbit." Part of the material that remains closer to Haumea can form a ring, and material further away can help form moons. "Because Haumea spins so quickly," Ortiz adds, "it is also possible that material is shed from the surface due to the centrifugal force, or maybe small collisions can trigger ejections of mass. This can also give rise to a ring and moons."

9. ONE MOON HAS WATER ICE—JUST LIKE HAUMEA.

Ortiz says that while the rings haven't transformed scientists' understanding of Haumea, they have clarified the orbit of its largest moon, Hi'iaka—it is equatorial, meaning it circles around Haumea's equator. Hi'iaka is notable for the crystalline water ice on its surface, similar to that on its parent body.

10. TRYING TO SEE HAUMEA FROM EARTH IS LIKE TRYING TO LOOK AT A COIN MORE THAN 100 MILES AWAY.

It's not easy to study Haumea. The dwarf planet, and other objects at that distance from the Sun, are indiscernible to all but the largest telescopes. One technique used by astronomers to study such objects is called "stellar occultation," in which the object is observed as it crosses in front of a star, causing the star to temporarily dim. (This is how exoplanets—those planets orbiting other stars—are also often located and studied.) This technique doesn't always work for objects beyond the orbit of Neptune, however; astronomers must know the objects' orbits and the position of the would-be eclipsed stars to astounding levels of accuracy, which is not always the case. Moreover, Ortiz says, their sizes are oftentimes very small, "comparable to the size of a small coin viewed at a distance of a couple hundred kilometers."

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