Posted on by Fraser Cain

Could Jupiter Become A Star?

Could Jupiter Become A Star?

NASA’s Galileo spacecraft arrived at Jupiter on December 7, 1995, and proceeded to study the giant planet for almost 8 years. It sent back a tremendous amount of scientific information that revolutionized our understanding of the Jovian system. By the end of its mission, Galileo was worn down. Instruments were failing and scientists were worried they wouldn’t be able to communicate with the spacecraft in the future. If they lost contact, Galileo would continue to orbit the Jupiter and potentially crash into one of its icy moons.

Galileo would certainly have Earth bacteria on board, which might contaminate the pristine environments of the Jovian moons, and so NASA decided it would be best to crash Galileo into Jupiter, removing the risk entirely. Although everyone in the scientific community were certain this was the safe and wise thing to do, there were a small group of people concerned that crashing Galileo into Jupiter, with its Plutonium thermal reactor, might cause a cascade reaction that would ignite Jupiter into a second star in the Solar System.

Hydrogen bombs are ignited by detonating plutonium, and Jupiter’s got a lot of hydrogen.Since we don’t have a second star, you’ll be glad to know this didn’t happen. Could it have happened? Could it ever happen? The answer, of course, is a series of nos. No, it couldn’t have happened. There’s no way it could ever happen… or is there?

Jupiter is mostly made of hydrogen, in order to turn it into a giant fireball you’d need oxygen to burn it. Water tells us what the recipe is. There are two atoms of hydrogen to one atom of oxygen. If you can get the two elements together in those quantities, you get water.

In other words, if you could surround Jupiter with half again more Jupiter’s worth of oxygen, you’d get a Jupiter plus a half sized fireball. It would turn into water and release energy. But that much oxygen isn’t handy, and even though it’s a giant ball of fire, that’s still not a star anyway. In fact, stars aren’t “burning” at all, at least, not in the combustion sense.

Jupiter as imaged by Michael Phillips on July 25th, 2009... note the impact scar discovered by Anthony Wesley to the lower left.
Jupiter as imaged by Michael Phillips on July 25th, 2009.

Our Sun produces its energy through fusion. The vast gravity compresses hydrogen down to the point that high pressure and temperatures cram hydrogen atoms into helium. This is a fusion reaction. It generates excess energy, and so the Sun is bright. And the only way you can get a reaction like this is when you bring together a massive amount of hydrogen. In fact… you’d need a star’s worth of hydrogen. Jupiter is a thousand times less massive than the Sun. One thousand times less massive. In other words, if you crashed 1000 Jupiters together, then we’d have a second actual Sun in our Solar System.

But the Sun isn’t the smallest possible star you can have. In fact, if you have about 7.5% the mass of the Sun’s worth of hydrogen collected together, you’ll get a red dwarf star. So the smallest red dwarf star is still about 80 times the mass of Jupiter. You know the drill, find 79 more Jupiters, crash them into Jupiter, and we’d have a second star in the Solar System.

There’s another object that’s less massive than a red dwarf, but it’s still sort of star like: a brown dwarf. This is an object which isn’t massive enough to ignite in true fusion, but it’s still massive enough that deuterium, a variant of hydrogen, will fuse. You can get a brown dwarf with only 13 times the mass of Jupiter. Now that’s not so hard, right? Find 13 more Jupiters, crash them into the planet?

As was demonstrated with Galileo, igniting Jupiter or its hydrogen is not a simple matter.
We won’t get a second star unless there’s a series of catastrophic collisions in the Solar System.
And if that happens… we’ll have other problems on our hands.

Posted on by Fraser Cain

Why Europa?

This artist's rendering shows NASA's Europa Clipper spacecraft, which is scheduled to launch in October, 2024. It'll have to contend with Jupiter's powerful radiation. Will a newly-found low-radiation path to Europa help? Image Credit: NASA/JPL

Forget Mars, the place we really want to go looking for life is Jupiter’s moon Europa. Dr. Mike Brown, a professor of planetary science at Caltech, explains what he finds so fascinating about this icy moon, and the potential we might find life swimming in its vast oceans.
Continue reading “Why Europa?”

Posted on by Fraser Cain

What are Hot Jupiters?

This artist's conception illustrates the brown dwarf named 2MASSJ22282889-431026. NASA's Hubble and Spitzer space telescopes observed the object to learn more about its turbulent atmosphere. Brown dwarfs are more massive and hotter than planets but lack the mass required to become sizzling stars. Their atmospheres can be similar to the giant planet Jupiter's. Spitzer and Hubble simultaneously observed the object as it rotated every 1.4 hours. The results suggest wind-driven, planet-size clouds. Image credit:
This artist's conception illustrates what a "hot jupiter" might look like.

When astronomers first discovered other planets, they were completely unlike anything we’ve ever found in the Solar System. These first planets were known as “hot jupiters”, because they’re giant planets – even more massive than Jupiter – but they orbit closer to their star than Mercury. Dr. Heather Knutson, a professor at Caltech explains these amazing objects.

“My name is Heather Knutson, and I’m a professor in the planetary science department here at Caltech. I study the properties of extrasolar planets, which are planets that orbit stars other than the sun, so mostly these are our closest exoplanetary neighbors. We’re not talking about planets in other galaxies – we’re mostly talking about planets which are in the same part of our own corner of our galaxy. So these are around some of the closest stars to the sun.”

What is a hot jupiter?

“The planets that I’ve found the most surprising, out of all of the ones I’ve discovered so far, I guess the sort of classic example, is that we’ve see these sorts of giant planets which are very similar to Jupiter, but orbit very much closer in than Mercury is to our sun, so these planets orbit their sun every two or three days and are absolutely getting roasted. We know that they couldn’t have formed there – they had to have formed farther out and migrated in, so what we’re still trying to understand are what are the forces that caused them to migrate in, whereas Jupiter seems to have migrated a little bit but more or less stayed put in our own solar system.”

What do hot jupiters mean for our understanding our own Solar System?

“The implications of these “hot jupiters” as we call them are actually huge for our own solar system, because if you want to know how many potentially habitable earthlike planets are out there, having one of these giant planets just rampage their way though the inner part of the planetary system, and it could toss out your habitable earth and put it into either a much closer orbit or a much further orbit. So knowing how things have moved around will tell you a lot about where you might find interesting planets.”

What is their atmosphere like?

“So, the atmospheres of hot jupiters are very exotic, by solar system standards. They typically have temperatures of a thousand to several thousand Kelvin, so at these temperatures these planets could have clouds of molten rock, for example. They have atmospheric compositions that would seem very exotic to us – they’re actually more similar to the compositions of relatively cool stars, so we have to adapt to describe these planets – we actually use stellar models to describe their atmospheres. We think that they’re also probably also tidally locked, which is very interesting because it means that one side of the planet is getting all of the heat and the other side is sort of in permanent night. And one thing we do is to try and understand the effect that has on the weather patterns on these planets, so you have winds that are pretty good at carrying that around the night side and mixing everything up, or do these planets have these just extreme temperature gradients between the day side and the night side.”

Hot Jupiter planet. Image Credit: ESA
Hot Jupiter planet. Image Credit: ESA

How’d they get there?

“So, we have a couple of theories for how hot jupiters may have ended up in their present day orbits. One theory is, that after they formed, that they were still embedded in the gas disc where they formed, and maybe they interacted with the disc as such that it kind of torqued and pulled them and so that’s kind of an early migration theory. There’s also a late migration theory version where when after the disc had gone away, these planets had interacted with a third body in the system, so maybe you had another distant massive planet or maybe you had a planet that was part of a binary star system, and those three body interactions excited a large orbital eccentricity in the innermost planet, and once it starts coming in closer to the star, the tides start to damp out the eccentricities, so what you end up with is something which is a gas giant planet in a very short period circular orbit.

So that’s kind of a more complicated story, but there are some clues in the data that might be true for at least a subset of the hot jupiters that we study.”

Posted on by Bob King

Will Jupiter’s Great Red Spot Turn into a Wee Red Dot?

At left, Photograph of Jupiter's enormous Great Red Spot in 1879 from Agnes Clerk's Book " A History of Astronomy in the 19th Century".

Watch out! One day it may just go away. Jupiter’s most celebrated atmospheric beauty mark, the Great Red Spot (GRS), has been shrinking for years.  When I was a kid in the ’60s peering through my Edmund 6-inch reflector, not only was the Spot decidedly red, but it was extremely easy to see. Back then it really did span three Earths. Not anymore. 

Drawing of Jupiter on Nov. 1, 1880 by French artist and astronomer Etienne Trouvelot
Drawing of Jupiter made on Nov. 1, 1880 by French artist and astronomer Etienne Trouvelot showing transiting moon shadows and a much larger Great Red Spot.

In the 1880s the GRS resembled a huge blimp gliding high above white crystalline clouds of ammonia and spanned 40,000 km (25, 000 miles) across. You couldn’t miss it even in those small brass refractors that were the standard amateur observing gear back in the day. Nearly one hundred years later in 1979, the Spot’s north-south extent has remained virtually unchanged, but it’s girth had shrunk to 25,000 km (15,535 miles) or just shy of two Earth diameters. Recent work done by expert astrophotographer Damian Peach using the WINJUPOS program to precisely measure the GRS in high resolution photos over the past 10 years indicates a continued steady shrinkage:

2003 Feb – 18,420km (11,445 miles)
2005 Apr – 18,000km (11,184)
2010 Sep – 17,624km (10,951)
2013 Jan – 16,954km (10,534)
2013 Sep – 15,894km (9,876)
2013 Dec – 15,302km (9,508) = 1.2 Earth diameters


Voyager 1 Jupiter time lapse animation, a reprocessed high-resolution view. Enlarge to full screen to see the GRS rotation best. Credit: NASA / JPL / Bjorn Jonsson / Ian Regan

If these figures stand up to professional scrutiny, it make one wonder how long the spot will continue to be a planetary highlight. It also helps explain why it’s  become rather difficult to see in smaller telescopes in recent years. Yes, it’s been paler than normal and that’s played a big part, but combine pallor with a hundred-plus years of downsizing and it’s no wonder beginning amateur astronomers often struggle to locate the Spot in smaller telescopes . This observing season the Spot has developed a more pronounced red color, but unless you know what to look for, you may miss it entirely unless the local atmospheric seeing is excellent.
Reprocessed view by Bjorn Jonsson of the Great Red Spot taken by Voyager 1 in 1979 reveals an incredible wealth of detail. Credit:
Reprocessed view by Bjorn Jonsson of the Great Red Spot made by Voyager 1 in 1979 reveals an incredible wealth of detail. The Spot is a vast, long-lived. hurricane-like storm located between opposing jet streams in Jupiter’s southern hemisphere. Click to enlarge. Credit: NASA/

Not only has the Spot been shrinking, its rotation period has been speeding up.  Older references give the period of one rotation at 6 days. John Rogers (British Astronomical Assn.) published a 2012 paper on the evolution of the GRS and discovered that between 2006 to 2012 – the same time as the Spot has been steadily shrinking – its rotation period has spun up to 4 days. As it shrinks, the storm appears to be conserving angular momentum by spinning faster the same way an ice skater spins up when she pulls in her arms.

Drawings by Cassini of what is presumably the Great Red Spot in 1665
Drawings by Cassini of what is presumably the Great Red Spot from 1665 to 1677. South is up. In size and shape it greatly resembles the current Red Spot. (From Amedee Guillemin’s “Le Ciel” 1877)

Rogers also estimated a max wind speed of 300 mph, up from about 250 mph in 2006.  Despite its smaller girth, this Jovian hurricane’s winds pack more punch than ever. Even more fascinating, the Great Red Spot may have even disappeared altogether from 1713 to 1830 before reappearing in 1831 as a long, pale “hollow”. According to Rogers, no observations or sketches of that era mention it. Surely something so prominent wouldn’t be missed. This begs the question of what happened in 1831. Was the “hollow” the genesis of a brand new Red Spot unrelated to the one first seen by astronomer Giovanni Cassini in 1665? Or was it the resurgence of Cassini’s Spot?

4-frame animation spans 24 Jovian days, or about 10 Earth days. The passage of time is accelerated by a factor of 600,000. Credit: NASA
14-frame animation showing the circulation of Jupiter’s atmosphere spans 24 Jovian days, or about 10 Earth days. The passage of time is accelerated by a factor of 600,000. Credit: Voyager 1 / NASA

Clearly, the GRS waxes and wanes but exactly what makes it persist? By all accounts, it should have dissipated after just a few decades in Jupiter’s turbulent environment, but a new model developed by Pedram Hassanzadeh, a postdoctoral fellow at Harvard University, and Philip Marcus, a professor of fluid dynamics at the University of California-Berkeley, may help to explain its longevity.  At least three factors appear to be at play:

* Jupiter has no land masses. Once a large storm forms, it can sustain itself for much longer than a hurricane on Earth, which plays itself out soon after making landfall.

* Eat or be eaten: A large vortex or whirlpool like the GRS can merge with and absorb energy from numerous smaller vortices carried along by the jet streams.

* In the Hassanzadeh and Marcus model, as the storm loses energy, it’s rejuvenated by vertical winds that transport hot and cold gases in and out of the Spot, restoring its energy. Their model also predicts radial or converging winds within the Spot that suck air from neighboring jet streams toward its center. The energy gained sustains the GRS.

Feb. 1 photo of Oval BA, a.k.a. Red Spot Jr. It's the first significant new red s[pt ever observed on Jupiter and located at longitude 332 degrees (Sys. II) The spot about half the width of the more familiar Great Red Spot. Credit: Christopher Go
Feb. 1 photo of Oval BA, a.k.a. Red Spot Jr. It’s the first significant new red spot ever observed on Jupiter and located at longitude 332 degrees (Sys. II) The spot about half the width of the more familiar Great Red Spot. Credit: Christopher Go
If the shrinkage continues, “Great” may soon have to be dropped from the Red Spot’s title. In the meantime, Oval BA (nicknamed Red Spot Jr.) and about half the size of the GRS, waits in the wings. Located along the edge of the South Temperate Belt on the opposite side of the planet from the GRS, Oval BA formed from the merger of three smaller white ovals between 1998 and 2ooo. Will it give the hallowed storm a run for its money? We’ll be watching.


Time-lapse of Jupiter’s atmospheric motions centered on the Great Red Spot photographed by Paolo Porcellana. Each cylindrical/spherical map of the planet is a mosaic of 4-6 pictures made with 11 and 14-inch telescopes.

Posted on by Fraser Cain

Weekly Space Hangout – January 24, 2014: LEGO Mars Rover & the Supernova We Missed in the Star Party!

Host: Fraser Cain

Special Guests: Stephen Pakbaz, designer of the LEGO Mars Rover Kit, and Ray Sanders from CosmoQuest, who is unboxing and building the kit as we hang out!

Astrojournalists: Morgan Rehnberg, Sondy Springmann, Elizabeth Howell, Casey Dreier, David Dickinson, Nicole Gugliucci, Mike Simmons
Continue reading “Weekly Space Hangout – January 24, 2014: LEGO Mars Rover & the Supernova We Missed in the Star Party!”

Posted on by David Dickinson

An Amazing Capture of Jupiter and its Moons

Astrophotographer Michael Phillips with the gear used to capture the Jupiter rotation animation. Credit-Michael Phillips

It’s always a thrill to watch the action at Jupiter, as its moons pass in front of and behind the gas giant planet. We wrote recently about this month’s opposition of Jove on January 5th, marking the start of the Jupiter evening viewing season for 2014. 

Astrophotographer Michael A. Philips also recently undertook a challenging series of sequences of Jupiter and its moons Io and Ganymede, with stunning results. You can see the motion of Jupiter’s rotation, the Great Red Spot and even a bit of cloud swirl as Io disappears behind Jupiter and Ganymede begins to transit in front and cast a shadow back onto the Jovian cloud tops.

Concerning the capture, Michael wrote on his blog:

“This night was a lucky night. I had not looked at the weather forecast enough to know if it would be good or not. Cold temps aside, I decided earlier in the day to set up and go out with the 14” f/4.5 scope named Akule. As an added bonus, Mitchell Duke tipped me off to a transit of the Jovian moon, Ganymede.”

Note that Jupiter and its moons are currently casting their shadows nearly straight back from our perspective. Expect that to change, however, in the coming months,as Jupiter heads towards eastern dusk quadrature on April 1st and we see the action from a sideways angle. Watch the video in full screen mode and you’ll note that Mike captured some detail on the surface of Ganymede as well! Generally, at the eyepiece, the moons of Jupiter disappear entirely due to low contrast against the bulk of the planet, with only the black dot of the shadow seen… this video capture gives the ingress of Ganymede at the start of the transit a great 3-D appearance.

Webcam imaging of planets has really taken off in the past decade, with backyard astronomers now routinely capturing images that far surpass professional and textbook images from just a decade prior. Great images can be taken using nothing more than a telescope, a laptop, free image stacking software such as Registax, and a webcam converted to fit into an eyepiece holder… you may find that you’ve got the gear sitting around to image Jupiter, tonight.

Mr. Phillips rig, however, is a little more advanced. He notes in the description of the video that he’s using a Flea3 camera from PointGrey Research with a 5x Barlow lens yielding a 9200mm focal length. He’s also shooting at 120 frames per second, and taking successive red, green and blue images for 30 seconds. Finally, a derotation of Jupiter – yes, it really rotates that quickly, even in a short sequence – is accomplished using a sophisticated program named WINJupos.

Video stacking gives processors the ability to “freeze” and nab the best moments of seeing from thousands of frames. Some imagers hand select frames one by one, though many programs, such as Registax, use algorithms to nab the best frames from a preselected percentage of the total shot.

Local seeing conditions also play a key role in image capturing.

“I moved far away from the house as possible, and I think that helped some,” Michael noted. “I also started cooling the spit out of the mirror, aggressively. Even when cooled for a few hours in the winter, the heat in the Pyrex mirror comes back. I think there’s a small heat engine inside the beast!”

For best results, imagers tend to go after planets when they’re at their highest in the sky, and viewed through the least amount of turbulent atmosphere. This is when a planet is transiting the local north to south meridian, and when it’s at opposition, which Jupiter is this month. At opposition, a planet transits at local midnight. The same goes for the best opportunities for visual observing as well.

Shadow transits of Jupiter’s moons are also just plain fun to watch. In an often unchanging universe, they offer a chance to see something unfolding in real time. Jupiter has the fastest rotation of any planet at 9.9 hours, and the large Galilean moons of Io, Europa, Ganymede and Callisto are tidally locked in their rotation, keeping one hemisphere permanently turned towards Jupiter like the Moon does orbiting the Earth. The inner three moons also keep a 1:2:4 orbital resonance, assuring you’ll never see more than three of the four Galilean moons transiting from your line of sight at once. You can see two of the inner three moons, plus Callisto in transit, but never all four at the same time! A triple transit last occurred on October 12th, 2013, and will next occur for observers in eastern Europe and Africa this year on June 3rd.

We’re also currently in the midst of a series of shadow transits for the outermost Galilean moon Callisto, which end in July 2016. Can you identify the different moons by the size and hue of shadows they cast? Sky & Telescope publishes a great table for the ingress and egress of Jupiter’s moons. You can also check them out using the freeware program Stellarium.

The double shadow transit of February 6th as seen at 11:22 UT. Created by the author using Starry Night Education software.
The double shadow transit of February 6th as seen at 11:22 UT. Created by the author using Starry Night Education software.

Can’t wait that long? A double shadow transit involving Europa and Callisto occurs in just a few weeks for western North America from 10:20 UT-12:44UT on the morning of February 6th, a chance for another stunning animation sequence…

Congrats to Michael Phillips on a great capture!