In a classic episode of this video series, I did the calculations for how fast the Earth is spinning.
We know the Earth is rotating, but why? Why is it spinning?
Why is everything in the Solar System spinning? And why is it mostly all spinning in the same direction?
It can’t be a coincidence. Look down on the Earth from above, and you’d see that it’s turning in a counter-clockwise direction. Same with the Sun, Mars and most of the planets.
4.54 billion years ago, our Solar System formed within a cloud of hydrogen not unlike the Orion Nebula, or the Eagle Nebula, with its awesome pillars of creation.
Then, it took some kick, like from the shockwave from a nearby supernova, and this set a region of the cold gas falling inward through its mutual gravity. As it collapsed, the cloud began to spin.
But why?
It’s the conservation of angular momentum.
Think about the individual atoms in the cloud of hydrogen. Each particle has its own momentum as it drifts through the void. As these atoms glom onto one another with gravity, they need to average out their momentum. It might be possible to average out perfectly to zero, but it’s really really unlikely.
Which means, there will be some left over. Like a figure skater pulling in her arms to spin more rapidly, the collapsing proto-Solar System with its averaged out particle momentum began to spin faster and faster.
This is the conservation of angular momentum at work.
As the Solar System spun more rapidly, it flattened out into a disk with a bulge in the middle. We see this same structure throughout the Universe: the shape of galaxies, around rapidly spinning black holes, and we even see it in pizza restaurants.
The Sun formed from the bulge at the center of this disk, and the planets formed further out. They inherited their rotation from the overall movement of the Solar System itself.
Over the course of a few hundred million years, all of the material in the Solar System gathered together into planets, asteroids, moons and comets. Then the powerful radiation and solar winds from the young Sun cleared out everything that was left over.
Without any unbalanced forces acting on them, the inertia of the Sun and the planets have kept them spinning for billions of years.
And they’ll continue to do so until they collide with some object, billions or even trillions of years in the future.
So are you still wondering, why does the Earth spin?
The Earth spins because it formed in the accretion disk of a cloud of hydrogen that collapsed down from mutual gravity and needed to conserve its angular momentum. It continues to spin because of inertia.
The reason it’s all the same direction is because they all formed together in the same Solar Nebula, billions of years ago.
On the Voyager spacecraft are the famous Voyager Golden Records, which send messages from planet Earth to … whatever or whoever may find it in the future. In celebration of Voyager 1 making it into interstellar space (read all the details here) a few friends put together a video to congratulate the spacecraft and the team. Neil deGrasse Tyson, Wil Wheaton, Carl Sagan’s son and others shared their messages to the Voyager 1 spacecraft.
Feel free to leave your message to Voyager in the (new and improved) comment section.
Hi everyone, I’m just performing a little experiment with Universe Today. We were previously using Disqus for comments on Universe Today, but I got a lot of concerns from readers.
So, I’m trying out a new system called Comments Evolved. This integrates comments from Google+, Facebook, Disqus and even WordPress if we want. I’m just enabling the Google+ version, because… everyone’s got a Google account.
If you want, I can enable the Facebook, Disqus and WordPress versions as well once I know this is working.
So why am I doing this? Why am I continuously making your life difficult with all this technology switcheroo?
Because managing comments on a public blog is like working at a SPAM factory. Behind the scenes here, we spend a MASSIVE amount of time killing SPAM, banning spambots, etc, etc. Not only do Nancy and I have to do it, but we actually have a few readers of Universe Today who we’ve deputized to help kill SPAM. And lots gets through.
In fact… we had turned off comments for posts older than 14 days because it was completely impossible to stay on top of the SPAM for all 15,000 articles within Universe Today.
So, in theory, by switching to this system… all the comments will have to go through Google’s SPAM filters first. You as users can identify comments as SPAM, and get them removed from the site, and teach Google how to do this better.
If it doesn’t work, we’ll just hack it out and go back to something else.
Feel free to drop me an email at [email protected] if you notice any bugs or have any further suggestions.
This artist's concept shows the general locations of NASA's two Voyager spacecraft. Voyager 1 (top) has sailed beyond our solar bubble into interstellar space, the space between stars. Its environment still feels the solar influence. Voyager 2 (bottom) is still exploring the outer layer of the solar bubble. Image credit: NASA/JPL-Caltech
This artist's concept shows the Voyager 1 spacecraft entering the space between stars. Interstellar space is dominated by plasma, ionized gas (illustrated here as brownish haze), that was thrown off by giant stars millions of years ago.Credit: NASA.
In a cosmically historic announcement, NASA says the most distant human made object — the Voyager 1 spacecraft — is in interstellar space, the space between the stars. It actually made the transition about a year ago.
“We made it!” said a smiling Dr. Ed Stone, Voyager’s Project Scientist for over 40 years, speaking at a briefing today. “And we did it while we still had enough power to send back data from this new region of space.”
While there is a bit of an argument on the semantics of whether Voyager 1 is still inside or outside of our Solar System (it is not farther out than the Oort Cloud — it will take 300 more years reach the Oort cloud and the spacecraft is closer to our Sun than any other star) the plasma environment Voyager 1 now travels through has definitely changed from what comes from our Sun to the plasma that is present in the space between stars.
But Stone now says the evidence in clear: Voyager 1 has made the transition.
“This conclusion is possible from the space craft’s plasma wave instrument,” Stone said. “The 36-year old probe is now sailing through uncharted waters of a new cosmic sea and it has brought us along for the journey.”
Voyager 1’s 36-year, 13 billion mile journey began in 1977.
Scientists thought that when the spacecraft had crossed over into interstellar space, the magnetic field direction would change. However, it turned out that didn’t happen, and scientists determined they needed to look at the properties of the plasma instead.
The Sun’s heliosphere is filled with ionized plasma from the Sun. Outside that bubble, the plasma comes from the explosions of other stars millions of years ago. The main tell-tail difference is the interstellar plasma is denser.
Unfortunately, the real instrument that was designed to make the measurements on the plasma quit working in the 1980’s, so scientists needed a different way to measure the spacecraft’s plasma environment to make a definitive determination of its location.
Instead they used the plasma wave instrument, located on the 10-meter long antennas on Voyager 1 and an unexpected “gift” from the Sun, a massive Coronal Mass Ejection.
The antennas have radio receivers at the ends – “like the rabbit ears on old television sets,” said Don Gurnett, who led the plasma wave science team at the University of Iowa. The CME erupted from the Sun in March 2012, and eventually arrived at Voyager 1’s location 13 months later, in April 2013. Because of the CME, the plasma around the spacecraft began to vibrate like a violin string.
The pitch of the oscillations helped scientists determine the density of the plasma. Stone said the particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere.
“Now that we have new, key data, we believe this is mankind’s historic leap into interstellar space,” said Stone, “The Voyager team needed time to analyze those observations and make sense of them. But we can now answer the question we’ve all been asking — ‘Are we there yet?’ Yes, we are.”
Artist’s impression of Voyager 1’s position on the sky when observed by the Very Long Baseline Array (VLBA) on February 21, 2013, at which point — according to NASA’s Jet Propulsion Laboratory — Voyager was already outside of our Solar System. The actual image from the data (enlarged section) is 0.5 arcseconds across. The radio signal as shown is a mere 1 milliarcsecond across. Credit: Alexandra Angelich, NRAO/AUI/NSF.
The plasma wave science team reviewed its data and found an earlier, fainter set of oscillations in October and November 2012 from other CMEs. Through extrapolation of measured plasma densities from both events, the team determined Voyager 1 first entered interstellar space in August 2012.
“We literally jumped out of our seats when we saw these oscillations in our data — they showed us the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble,” Gurnett said. “Clearly we had passed through the heliopause, which is the long-hypothesized boundary between the solar plasma and the interstellar plasma.”
At that time, Stone said, “We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space,” adding that the data are changing in ways that the team didn’t expect, “but Voyager has always surprised us with new discoveries.”
Now, after further review, the Voyager team generally accepts the August 2012 date as the date of interstellar arrival. The charged particle and plasma changes were what would have been expected during a crossing of the heliopause. This reinforces that definitive science results don’t always come fast.
“The team’s hard work to build durable spacecraft and carefully manage the Voyager spacecraft’s limited resources paid off in another first for NASA and humanity,” said Suzanne Dodd, Voyager project manager, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We expect the fields and particles science instruments on Voyager will continue to send back data through at least 2020. We can’t wait to see what the Voyager instruments show us next about deep space.”
There has been some back and forth about whether Voyager 1 was in or out of the Solar System. As we said, it was first questioned in August of 2012, with more speculation in December 2012, then in March of 2013 a paper by William Webber and F.B. McDonald claimed Voyager 1 had exited the Solar System the previous December, but Stone insisted the data wasn’t positive yet. Then about a month ago a paper came out by Marc Swisdak from the University of Maryland saying Voyager 1 was out of the solar system, but at that point Ed Stone and the Voyager team put out a statement saying they were still making that determination.
Today, Gurnett revealed that the timing of all scientists being in “official” agreement was off due to the timing of the review process for scientific papers. “Our paper was submitted a month before theirs, they just got through the review cycle before ours,” he said. “But theirs was basically a theory paper.”
Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. A fortuitous planetary alignment that only happens every 176 years enabled the two spacecraft to join together to reach all the outer planets in a 12 year time period. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft. It is about 9.5 billion miles (15 billion kilometers) away from our Sun.
Voyager mission controllers still talk to or receive data from Voyager 1 and Voyager 2 every day, though the emitted signals are currently very dim, at about 23 watts — the power of a refrigerator light bulb. By the time the signals get to Earth, they are a fraction of a billion-billionth of a watt. Data from Voyager 1’s instruments are transmitted to Earth typically at 160 bits per second, and captured by 34- and 70-meter NASA Deep Space Network stations. Traveling at the speed of light, a signal from Voyager 1 takes about 17 hours to travel to Earth. After the data are transmitted to JPL and processed by the science teams, Voyager data are made publicly available.
“Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and adding a new chapter in human scientific dreams and endeavors,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “Perhaps some future deep space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their journey.”
Scientists do not know when Voyager 1 will reach the undisturbed part of interstellar space where there is no influence from our Sun. They also are not certain when Voyager 2 is expected to cross into interstellar space, but they believe it is not very far behind.
“In a sense this is only really the beginning. We’re now going into a completely alien environment and what Voyager is going to discover truly unknown,” said Gary Zank, from the Department of Space Sciences at the University of Alabama, Huntsville, speaking at today’s press conference.
While Voyager 1 will keep going, we will not always be able to communicate with it, as we do now. In 2025 all instruments will be turned off, and the science team will be able to operate the spacecraft for about 10 years after that to just get engineering data. Voyager 1 is aiming toward the constellation Ophiuchus. In the year 40,272 AD, Voyager 1 will come within 1.7 light years of an obscure star in the constellation Ursa Minor (the Little Bear or Little Dipper) called AC+79 3888. It will swing around the star and orbit about the center of the Milky Way, likely for millions of years.
A detailed look at a nebula, known as the Bubble Nebula, or Sharpless 162 or NGC 7635, was taken with with a QHY9 Camera and a Meade LX200 GPS 12 in" telescope. Credit and copyright: J-P Metsävainio.
We’ve featured the unique 3-D work of J-P Metsävainio previously, but it’s time to check in and see what he’s been working on lately. Metsävainio creates incredible 3-D animations from his own astronomical images, which he calls “3-D experiments” that are a mixture of science and an artistic impression. “I collect distance and other information before I do my 3-D conversion,” he told Universe Today via email earlier this year. “Usually there are known stars, coursing the ionization, so I can place them at right relative distance. If I know a distance to the nebula, I can fine tune distances of the stars so, that right amount of stars are front and behind of the object.”
Above is the animation of the Bubble Nebula, below is his extremely detailed image:
His observations and images are simply stunning, but he says his 3-D animations are “a personal vision about shapes and volumes, based on some scientific data and an artistic impression.”
An artist's conception of Juno's October 9th flyby of the Earth. (Credit: NASA/JPL -Caltech).
Psst! Live in South Africa and read Universe Today? Then you might just get a peak at the Juno spacecraft as it receives a boost from our fair planet on the evening of October 9th, 2013.
Launched from Cape Canaveral Air Force Station on August 5th, 2011 atop an Atlas 5 rocket in a 551 configuration, Jupiter-bound Juno is approaching the Earth from interior to its orbit over the next month. Its closest approach to the Earth during its October 9th flyby will occur at 19:21 Universal Time (UT) which is 3:21 PM Eastern Daylight Saving Time. The spacecraft will pass 559 kilometres over the South Atlantic to a point 200 kilometres off of the southeastern coast of South Africa at latitude -34.2° south & longitude 34° east.
For context, this is just about 25% higher than the International Space Station orbits at an average of 415 kilometres above the Earth. The ISS is 108.5 metres across on its longest dimension, and we wouldn’t be surprised if Juno were a naked eye object for well placed observers watching from a dark sky site around Cape Town, South Africa. Especially if one of its three enormous 8.9 metre long solar panels were to catch the Sun and flare Iridium-style!
Two minutes before closest approach, Juno will experience the only eclipse of its mission, passing into the umbra of Earth’s shadow for about 20 minutes. Chris Peat at Heavens-Above also told Universe Today that observers in India are also well-placed to catch sight of Juno with binoculars after it exits the Earth’s shadow.
Juno passed its half-way mark to Jupiter last month on August 12th when the “odometer clicked over” to 9.464 astronomical units. Juno will enter orbit around Jupiter on July 4th, 2016. Juno will be the second spacecraft after Galileo to permanently orbit the largest planet in our solar system.
The passage of Juno through the Earth’s shadow on October 9th, 2013. (Credit and Copyright: Heavens-Above, used with permission).
Catching a flyby of Juno will be a unique event. Unfortunately, the bulk of the world will miss out, although you can always vicariously fly along with Juno with Eyes on the Solar System. Juno is currently moving about 7 km/s relative to the Earth, and will move slightly faster than the ISS in its apparent motion across the sky from west to east before hitting Earth’s shadow. This slingshot will give Juno a 70% boost in velocity to just under 12km/s relative to Earth, just slower than Pioneer 10’s current motion relative to the Sun of 12.1km/s.
At that speed, Juno will be back out past the Moon in about 10 hours after flyby. There’s a chance that dedicated imagers based along North American longitudes could still spy Juno later that evening.
Juno approaches the Earth from the direction of the constellation Libra and will recede from us in the direction of the constellation Perseus on the night of October 9th.
The ground track covered by Juno as it passes by the Earth. (Credit & Copyright: Heavens-Above, used with permission).
There’s also a precedent for spotting such flybys previous. On August 18th, 1999, NASA’s Cassini spacecraft made a flyby of the Earth at 1,171 kilometres distant, witnessed by observers based in the eastern Pacific region. Back then, a fuss had been raised about the dangers that a plutonium-powered spacecraft might posed to the Earth, should a mis-calculation occur. No such worries surround Juno, as it will be the first solar-powered spacecraft to visit the outer solar system.
And NASA wants to hear about your efforts to find and track Juno during its historic 2013 flyby of the Earth. JPL Horizons lists an ephemeris for the Juno spacecraft, which is invaluable for dedicated sky hunters. You can tailor the output for your precise location, then aim a telescope at low power at the predicted right ascension and declination at the proper time, and watch. Precise timing is crucial; I use WWV shortwave radio broadcasting out of Fort Collins, Colorado for ultra-precise time when in the field.
As of this writing, there are no plans to broadcast the passage of Juno live, though I wouldn’t be surprised if someone like Slooh decides to undertake the effort. Also, keep an eye on Heavens-Above, as they may post sighting opportunities as well. We’ll pass ‘em along if they surface!
Late Breaking: And surface they have… a page dedicated to Juno’s flyby of Earth is now up on Heavens-Above.
Juno is slated to perform a one year science mission studying the gravity and magnetic field of Jupiter as well as the polar magnetosphere of the giant planet. During this time, Juno will make 33 orbits of Jupiter to complete its primary science mission. Juno will study the environs of Jupiter from a highly inclined polar orbit, which will unfortunately preclude study of its large moons. Intense radiation is a primary hazard for spacecraft orbiting Jupiter, especially one equipped with solar panels. Juno’s core is shielded by one centimetre thick titanium walls, and it must thread Jupiter’s radiation belts while passing no closer than 4,300 kilometres above the poles on each pass. One run-in with the Io Plasma Torus would do the spacecraft in. Like Galileo, Juno will be purposely deorbited into Jupiter after its primary mission is completed in October 2017.
If you live in the right location, be sure to check out Juno as it visits the Earth, one last time. We’ll keep you posted on any live broadcasts or any further info on sighting opportunities as October 9th draws near!
– Got pics of Juno on its flyby of the Earth? Send ’em in to Universe Today!
– You can also follow the mission on Twitter as @NASAJuno.
A colorful view of the Milky Way based on a new 3-D structure created by astronomers. "Due to our position within the disk it is difficult to identify the detailed structure of the inner galaxy," the Max Planck Institute for Extraterrestrial Physics said in a statement. Credit: MPE
Thanks to a new analysis of pictures obtained by a telescope in Chile, astronomers are gaining a better understanding of how the Milky Way formed and how our home galaxy has changed over the years.
Here’s how the project worked:
– The European Southern Observatory’s Visible and Infrared Survey Telescope for Astronomy (VISTA) 4.1-meter telescope took near-infrared pictures of the bulge of the Milky Way during the Variables in the Via Lactea public survey.
– Using the public data, scientists at the Max Planck Institute for Extraterrestrial Physics (MPE) created a three-dimensional star map of the inner regions of the Milky Way.
Milky Way. Image credit: NASA
– Their findings were that the bulge in the center is shaped like a box or a peanut, with characteristics such as an “elongated bar”. It’s the first time such an accurate 3-D map of the inner universe was constructed, the science team said.
“This indicates that the Milky Way was originally a pure disk of stars, which then formed a thin bar, before buckling into the box/peanut shape seen today,” MPE stated. “The new map can be used for more detailed studies of the dynamics and evolution of our Milky Way.”
Among other conclusions, this helps confirm the fairly recent finding that the Milky Way is a barred spiral galaxy, rather than just a spiral galaxy.
An atlas of the asteroid, Vesta, created from mosaics of 10 000 images from Dawn’s framing camera (FC) instrument, taken during the Dawn Mission’s Low Altitude Mapping Orbit (LAMO) an altitude of around 135 miles (210 kilometres). Credit: European Space Agency
Now’s your big chance to get up close and personal with Vesta, one of the largest asteroids in the solar system.
A new atlas has been released based on 10,000 images from the Dawn mission‘s framing camera instrument, which took the pictures from an average altitude of about 131 miles (210 kilometers). Each map has a scale of 1 centimetre to 2 kilometres (roughly a scale of 0.4 inches : 1.2 miles).
“Creating the atlas has been a painstaking task – each map sheet of this series has used about 400 images,” stated Thomas Roatsch, who is with the German Aerospace Center (DLR) Institute of Planetary Research and led the work.
This image from NASA’s Dawn spacecraft shows a close up of part of the rim around the crater Canuleia on the giant asteroid Vesta. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown
“The atlas shows how extreme the terrain is on such a small body as Vesta. In the south pole projection alone, the Severina crater contours reaches a depth of 18 kilometres [11 miles]; just over 100 kilometres [62 miles] away the mountain peak towers 7 kilometres [4.3 miles] above the … reference level.”
Astrobotic's model rover explores a mine on Earth to train for lunar lava tunnels (Video screenshot)
Ever since (and most likely long before) the first tantalizing glimpses of a lunar lava tube and skylight were captured by Japan’s Kaguya spacecraft in 2009, scientists have been dreaming of ways to explore inside these geological treasures. Not only would they provide valuable information on the movement of ancient lunar lava flows, but they could also be great places for future human explorers to set up camp and be well-protected from dangerous solar and cosmic radiation.
But before human eyes will ever peer into the darkness of a lava tube on the Moon, robotic rovers will roll along their silent floors — at least, they will if Google Lunar XPRIZE competitor Astrobotic has anything to say about it.
Last month, engineer and Astrobotic CEO Dr. Red Whitttaker talked to NASA about why they want to explore a Moon cave and the history and progress of their project. Check it out below:
“Something so unique about the lava tubes is that they are the one destination that combines the trifecta of science, exploration, and resources.”
– Dr. William “Red” Whittaker, CEO Astrobotic Technology, Inc.
The international Google Lunar XPRIZE aims to create a new “Apollo” moment for a new generation by driving continuous lunar exploration with $40 million in incentive-based prizes. In order to win, a private company must land safely on the surface of the Moon, travel 500 meters above, below, or on the lunar surface, and send back two “Mooncasts” to Earth… all by Dec. 31, 2015.
Astrobotic Technology Inc. is a Pittsburgh-based company that delivers affordable space robotics technology and planetary missions. Spun out of Carnegie Mellon University’s Robotics Institute in 2008, Astrobotic is pioneering affordable planetary access that promises to spark a new era of exploration, science, tourism, resource utilization and mining. (Source)
The Sun formed from the bulge at the center of this disk, and the planets formed further out. They inherited their rotation from the overall movement of the Solar System itself. 
The Earth spins because it formed in the accretion disk of a cloud of hydrogen that collapsed down from mutual gravity and needed to conserve its angular momentum. It continues to spin because of inertia.
