Marvelous Jupiter at biggest and brightest of 2017 right now

Friday, April 7, 2017, 2:56 PM - Planet Jupiter is at its closest point to Earth of the year, and as a result, it is shining big and bright in our night sky. Here's who can see it, and what two cameras in space are showing us from this marvelous giant.

Jupiter portrait from Hubble

Jupiter reached Opposition on Friday, April 7, 2017, when it was on the exact opposite side of Earth from the Sun, and at its closest point to Earth of the year.

When this happens, every 13 months or so, it is the perfect time to aim the Hubble Space Telescope at the giant planet, to capture the greatest amount of details from its cloud bands and swirling storms.

This time around was no different, as shown by this new portrait of Jupiter, snapped by Hubble on Monday, April 3.

Jupiter, on approach to Opposition 2017, from the Hubble Space Telescope's Wide Field Camera 3. Credit: NASA, ESA, and A. Simon (GSFC)

The above image joins the catalogue of Hubble images known as OPAL - the Outer Planets Atmospheres Legacy program.

As NASA's Katrina Jackson tells us in the video, above, this image is also part of a set which will go into making a new global map of the gas giant's features, so watch out, in the near future, for a brand new digital globe of the planet to debut.

In the mean time, though, this new image is already adding to the body of science we have on Jupiter, specifically about the ongoing shrinking of the Great Red Spot.

This time-lapse animation features Hubble images of Jupiter's Great Red Spot, from 1992 to 2017. Credits: Z. Levay (STScI)/R. Garner (NASA Goddard)

The Great Red Spot is an immense, persistent anticyclonic storm, that churns away at 22 degrees South latitude on Jupiter. 

It is called an anticyclonic storm because it rotates in the opposite direction that a traditional storm should - counter-clockwise, when a southern hemisphere storm should rotate clockwise. What that means is, rather than winds swirling inward towards a low-pressure centre, the Great Red Spot (at least at the top, where we can see it) has winds that swirl outward, away from a high pressure centre.

It is so persistent that, for as long as astronomers have been able to get a clear view of it among Jupiter's cloud features, with observations dating back at least 150 years, it has always been there. 

And it is so immense that, at one time, it would fit three Earth's inside it, and still have room to spare. Those days have long passed, though, since the storm is shrinking, and has been for at least a century. The oldest estimates, from observations with Earth-based telescopes, put it at over 40,000 km across (Earth's diameter is 12,700 km). Then, in 1972, when Voyager 1 gave us our first up-close look at the Great Red Spot, it was around 23,000 km across. Measurements from Hubble had it at nearly 21,000 km in 1995, then just shy of 18,000 km across in 2009, and down to just 16,400 km in 2014. Now, in 2017, it's even smaller, roughly the size of Earth.

Astronomers still are not sure why the Great Red Spot is shrinking, but further observations may hold clues that solve the mystery.

Skimming above Jupiter's cloud-tops

Hubble's views of Jupiter are beautiful, but we have an even closer camera to snap images with, on board NASA's Juno spacecraft.

JunoCam image from March 27, 2017, from roughly one Earth-diameter (12,700 km) above the planet's clouds. Credits: NASA/JPL-Caltech/SwRI/MSSS/ Roman Tkachenko

This image captures a portion of Jupiter's cloud bands near the terminator between day and night, giving a high-contrast look at the cloud tops.

According to NASA, and John Rogers, the citizen scientist who identified the point of interest featured here:

This publicly selected target is called "STB Spectre." The ghostly bluish streak across the right half of the image is a long-lived storm, one of the few structures perceptible in these whitened latitudes where the south temperate belt of Jupiter would normally be. The egg-shaped spot on the lower left is where incoming small dark spots make a hairpin turn.

This latest pass for Juno, on March 27, 2017, was its fifth close-up since the spacecraft arrived in orbit of Jupiter on the night of July 4, 2016, by Eastern Daylight Time. It has been on a long-distance orbit around the planet since that arrival, and although plans were made to shift Juno into a closer orbit for science work, an engine problem has forced the mission team to keep the spacecraft in its current orbit, very likely for the rest of its time at Jupiter.

That schedule gives us close-up images of Jupiter every 53 days or so, so the next pass will be on May 19, 2017.

Did you see Jupiter at Opposition?

Sources: NASA | ESA/Hubble | NASA Juno