Auroras - Blog Posts
We Need Your Help to Find STEVE
Glowing in mostly purple and green colors, a newly discovered celestial phenomenon is sparking the interest of scientists, photographers and astronauts. The display was initially discovered by a group of citizen scientists who took pictures of the unusual lights and playfully named them "Steve."
When scientists got involved and learned more about these purples and greens, they wanted to keep the name as an homage to its initial name and citizen science discoverers. Now it is STEVE, short for Strong Thermal Emission Velocity Enhancement.
Credit: ©Megan Hoffman
STEVE occurs closer to the equator than where most aurora appear – for example, Southern Canada – in areas known as the sub-auroral zone. Because auroral activity in this zone is not well researched, studying STEVE will help scientists learn about the chemical and physical processes going on there. This helps us paint a better picture of how Earth's magnetic fields function and interact with charged particles in space. Ultimately, scientists can use this information to better understand the space weather near Earth, which can interfere with satellites and communications signals.
Want to become a citizen scientist and help us learn more about STEVE? You can submit your photos to a citizen science project called Aurorasaurus, funded by NASA and the National Science Foundation. Aurorasaurus tracks appearances of auroras – and now STEVE – around the world through reports and photographs submitted via a mobile app and on aurorasaurus.org.
Here are six tips from what we have learned so far to help you spot STEVE:
1. STEVE is a very narrow arc, aligned East-West, and extends for hundreds or thousands of miles.
Credit: ©Megan Hoffman
2. STEVE mostly emits light in purple hues. Sometimes the phenomenon is accompanied by a short-lived, rapidly evolving green picket fence structure (example below).
Credit: ©Megan Hoffman
3. STEVE can last 20 minutes to an hour.
4. STEVE appears closer to the equator than where normal – often green – auroras appear. It appears approximately 5-10° further south in the Northern hemisphere. This means it could appear overhead at latitudes similar to Calgary, Canada. The phenomenon has been reported from the United Kingdom, Canada, Alaska, northern US states, and New Zealand.
5. STEVE has only been spotted so far in the presence of an aurora (but auroras often occur without STEVE). Scientists are investigating to learn more about how the two phenomena are connected.
6. STEVE may only appear in certain seasons. It was not observed from October 2016 to February 2017. It also was not seen from October 2017 to February 2018.
Credit: ©Megan Hoffman
STEVE (and aurora) sightings can be reported at www.aurorasaurus.org or with the Aurorasaurus free mobile apps on Android and iOS. Anyone can sign up, receive alerts, and submit reports for free.
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Magnetospheres: How Do They Work?
The sun, Earth, and many other planets are surrounded by giant magnetic bubbles.
Space may seem empty, but it’s actually a dynamic place, dominated by invisible forces, including those created by magnetic fields. Magnetospheres – the areas around planets and stars dominated by their magnetic fields – are found throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are mostly spewed out by the sun, but can also come from interstellar space. Along with atmospheres, they help protect the planets’ surfaces from this harmful radiation.
It’s possible that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, so finding magnetospheres around other planets is a big step toward determining if they could support life.
But not all magnetospheres are created equal – even in our own backyard, not all planets in our solar system have a magnetic field, and the ones we have observed are all surprisingly different.
Earth’s magnetosphere is created by the constantly moving molten metal inside Earth. This invisible “force field” around our planet has an ice cream cone-like shape, with a rounded front and a long, trailing tail that faces away from the sun. The magnetosphere is shaped that way because of the constant pressure from the solar wind and magnetic fields on the sun-facing side.
Earth’s magnetosphere deflects most charged particles away from our planet – but some do become trapped in the magnetic field and create auroras when they rain down into the atmosphere.
We have several missions that study Earth’s magnetosphere – including the Magnetospheric Multiscale mission, Van Allen Probes, and Time History of Events and Macroscale Interactions during Substorms (also known as THEMIS) – along with a host of other satellites that study other aspects of the sun-Earth connection.
Mercury, with a substantial iron-rich core, has a magnetic field that is only about 1% as strong as Earth’s. It is thought that the planet’s magnetosphere is stifled by the intense solar wind, limiting its strength, although even without this effect, it still would not be as strong as Earth’s. The MESSENGER satellite orbited Mercury from 2011 to 2015, helping us understand our tiny terrestrial neighbor.
After the sun, Jupiter has by far the biggest magnetosphere in our solar system – it stretches about 12 million miles from east to west, almost 15 times the width of the sun. (Earth’s, on the other hand, could easily fit inside the sun.) Jupiter does not have a molten metal core like Earth; instead, its magnetic field is created by a core of compressed liquid metallic hydrogen.
One of Jupiter’s moons, Io, has intense volcanic activity that spews particles into Jupiter’s magnetosphere. These particles create intense radiation belts and the large auroras around Jupiter’s poles.
Ganymede, Jupiter’s largest moon, also has its own magnetic field and magnetosphere – making it the only moon with one. Its weak field, nestled in Jupiter’s enormous shell, scarcely ruffles the planet’s magnetic field.
Our Juno mission orbits inside the Jovian magnetosphere sending back observations so we can better understand this region. Previous observations have been received from Pioneers 10 and 11, Voyagers 1 and 2, Ulysses, Galileo and Cassini in their flybys and orbits around Jupiter.
Saturn’s moon Enceladus transforms the shape of its magnetosphere. Active geysers on the moon’s south pole eject oxygen and water molecules into the space around the planet. These particles, much like Io’s volcanic emissions at Jupiter, generate the auroras around the planet’s poles. Our Cassini mission studies Saturn’s magnetic field and auroras, as well as its moon Enceladus.
Uranus’ magnetosphere wasn't discovered until 1986 when data from Voyager 2’s flyby revealed weak, variable radio emissions. Uranus’ magnetic field and rotation axis are out of alignment by 59 degrees, unlike Earth’s, whose magnetic field and rotation axis differ by only 11 degrees. On top of that, the magnetic field axis does not go through the center of the planet, so the strength of the magnetic field varies dramatically across the surface. This misalignment also means that Uranus’ magnetotail – the part of the magnetosphere that trails away from the sun – is twisted into a long corkscrew.
Neptune’s magnetosphere is also tilted from its rotation axis, but only by 47. Just like on Uranus, Neptune’s magnetic field strength varies across the planet. This also means that auroras can be seen away from the planet’s poles – not just at high latitudes, like on Earth, Jupiter and Saturn.
Does Every Planet Have a Magnetosphere?
Neither Venus nor Mars have global magnetic fields, although the interaction of the solar wind with their atmospheres does produce what scientists call an “induced magnetosphere.” Around these planets, the atmosphere deflects the solar wind particles, causing the solar wind’s magnetic field to wrap around the planet in a shape similar to Earth’s magnetosphere.
What About Beyond Our Solar System?
Outside of our solar system, auroras, which indicate the presence of a magnetosphere, have been spotted on brown dwarfs – objects that are bigger than planets but smaller than stars.
There’s also evidence to suggest that some giant exoplanets have magnetospheres. As scientists now believe that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, finding magnetospheres around exoplanets is a big step in finding habitable worlds.
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What does the sun do at the Pole !?
A collection of Pokémon doodles from memory :)
I’m a Northern Hemisphere dweller, so I thought it would be fun to cover Southern Hemisphere stars and constellations in this episode! I also coulsnt’ resist talking about Aurora Australis and Steve, the hot new atmospheric phenomenon all the young people are talking about.
Below the cut, I have the glossary, transcript, sources, and music credits. I take topic suggestions from Tumblr messages, or you can tweet at me on Twitter at @HDandtheVoid, or you can ask me to my face if you know me. Please subscribe on iTunes, rate my podcast and maybe review it, and tell friends if you think they’d like to hear it!
(My thoughts on the next episode are Chuck Yeager, Stephen Hawking and his theories, the opposition of Mars, or famous comets. The next episode will go up May 14th or 21st!)
Glossary
Bayer designation - a way to classify stars based on their relative brightness within a constellation. A specific star is identified by a Greek letter, followed by the genitive form of the constellation's Latin name.
circumpolar - appearing to orbit one of the Earth’s poles. For stars and constellations, this means they are above the horizon at all times in certain latitudes.
irregular galaxy - an asymmetrical galaxy shape, where the galaxy lacks a central supermassive black hole.
Script/Transcript
Sources
Orion from the Southern Hemisphere via EarthSky (Mar 2017)
How to Spot Sky Landmarks: Big Dipper and Southern Cross via Space.com (Apr 2012)
Locate Cassiopeia the Queen via EarthSky (February 2018)
Small Magellanic Cloud orbits Milky Way via EarthSky (Oct 2017)
Nubecula via LatDict
Early star catalogues of the southern sky via Astronomy and Astrophysics (2011)
Catalog of Southern Stars via the University of Oklahoma
Edmond Halley via Royal Museums Greenwich
Finding south using the Southern Cross via Museum of Applied Arts and Sciences (Jan 2013)
List of 88 official constellations via the Astronomical Society of Southern Africa
Alpha Centauri system, closest to sun via EarthSky (May 2017)
Hadar is a southern pointer star via EarthSky (April 2017)
Aurora Australis forecast service
Video of aurora australis via Global News Canada (April 2018)
Aurora Steve via Global News Canada (March 2018)
Bagnall, Philip M. “Crux.” In The Star Atlas Companion: What You Need to Know About the Constellations. Springer Science+Business Media: New York, 2012 (183-7). Located in Google Books Preview [accessed May 1, 2018].
Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity
Filler Music: ‘Mace Spray’ by The Jezabels off their EP Dark Storm.
Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught
In the ancient world (and, honestly, today too) there’s nothing spookier than the sky doing something weird. Auroras, meteors, comets, and eclipses all fell under the category of scary, prophetic bad omens, but don’t worry! In this podcast I explain what they are! There are also some opportunities to see these astronomical events in action coming up. The annual Perseid meteor shower reaches its peak August 11-13 and there will be a total eclipse of the Sun (or a partial eclipse, depending where you’re viewing it from) across North America on August 21, 2017.
Below the cut are sources, music credits, vocabulary list, and the transcript of this episode. Check out the glossary, it’s a big one! There are also some cool eclipse-viewing resources I’ll highlight so you can view this phenomenon safely.
Let me know what you think I should research by messaging me here, tweeting at me at @HDandtheVoid, or asking me to my face if you know me in real life. And please check out the podcast on iTunes, rate it or review it if you’d like, subscribe, and maybe tell your friends about it if you think they’d like to listen!
(My thoughts on the next episode were spectroscopy, probes through the ages, and the transit of Venus. Let me know by the 2nd and I’ll have the next podcast up on August 14th, barring any delays due to trip fatigue!)
Glossary
auroras - a light display that occurs when a magnetosphere is sufficiently disturbed by solar wind that charged particles scatter into the upper atmosphere and lose their energy.
comet - a small, icy body that orbits the Sun. When its orbit takes it close to the Sun, the comet warms up and releases gases and debris that produce a visible atmosphere, sometimes called the comet’s tail.
corona - the hot outer atmosphere of the Sun.
eclipse - when three celestial bodies line up so that one obstructs the visibility of the other two. A solar eclipse can be partial (only part of the Sun is obscured by the Moon), total (all of the Sun is hidden by the Moon), or annular ( the Moon is close to Earth and appears too small to completely cover the Sun completely).
Exeligmos cycle - a cycle that is 3 times the saros cycle, or 669 months. It is more accurate means of predicting eclipses and additionally predicts eclipses that will be visible from a location close to the initial eclipse.
Inex cycle - a cycle of 28 years and 345 days long used to predict an eclipse that’s visible in the opposite hemisphere. For example, if an eclipse happens in the Northern hemisphere, one Inex cycle later there will be an eclipse visible in the Southern hemisphere. The Inex cycle does not ensure that both kinds of eclipses will be of the same type.
meteor - a small rocky or metallic body in space, smaller than asteroids. Contact with the Earth’s atmosphere causes a meteor to burn up in a streak of light. Many meteors entering the atmosphere within a few minutes of each other is called a meteor shower. If a meteor impacts on Earth’s surface without burning up, it is then classified as a meteorite.
penumbra - a region where only a portion of the light source is obscured. When the light source is completely blocked, this darkest part of a shadow is called the umbra.
perihelion - an object’s closest approach to the Sun in its orbit. Its greatest distance from the Sun is called its aphelion.
perigee - a satellite’s closest approach to the Earth in its orbit. Its greatest distance from Earth is called its apogee.
radiant - the point in the sky where objects appear to come from. For example, the Perseid meteor shower appears to come from the constellation Perseus.
Saros cycle - a cycle of 223 months that is used to predict eclipses.
solar prominence - a large, bright feature anchored to the Sun's surface and extend outwards into the Sun's corona. A prominence forms in about a day out of plasma, a hot gas made of electrically charged hydrogen and helium. Stable prominences may last for several months, looping hundreds of thousands of miles into space as plasma flows along a structure of the Sun’s magnetic field that has burst outward, releasing the plasma.
syzygy - the straight-line alignment of three celestial bodies.
Script/Transcript
Sources
Perseids via EarthSky
Perseids via NASA
Meteor showers and viewing tips via StarDate
Comet Swift-Tuttle via NASA
My local library’s information and recommended reading list for learning about eclipses. Love you, Multnomah County!
Map of the Path of Totality across the United States
Solar eclipse map and calendar via the Exploratorium website
Free eclipse glasses at libraries via Lunar and Planetary Institute
Guide to making a pinhole camera to view the eclipse via NASA
Historical eclipses via NASA
Historical eclipses via Astronomy Magazine
“Even if the Moon, however, does sometimes cover the Sun entirely, the eclipse does not have duration or extension; but a kind of light is visible about the rim which keeps the shadow from being profound and absolute.”
Solar prominence via NASA
Solar flares via NASA
Fred Espenak’s guide to eclipses. He’s a former NASA astrophysicist who’s credited with all the eclipse predictions so I trust him.
Some good but confusing charts on solar eclipse Saros cycles via NASA
“Van den Bergh placed all 8,000 solar eclipses in von Oppolzer's Canon der Finsternisse (1887) into a large two-dimensional matrix. Each Saros series was arranged as a separate column containing every eclipse in chronological order. The individual Saros columns were then staggered so that the horizontal rows each corresponded to different Inex series.”
A Danish webpage on calculating eclipses
Hawks, Ellison. The Boy’s Book of Astronomy. Frederick A. Stokes Co: New York, 1914. Located in Google Books preview. (Heads up, this is a fairly racist source.)
Richard Cohen. Chasing the Sun. Random House: NY, 2010.
Robert A. Henning: “different forms, wavering, many colours diffusing and changing, sometimes far away, sometimes filling the heavens around and above, plunging great dropping spears and sheets of colour earthward towards your very head as though a great hand were dropping colour like burning oil” (43).
Ernest W. Hawkes: “whistling, crackling noise” (44).
Jeremy Belknap: “like running one’s thumb and forefinger down a silk scarf” (44).
Intro Music: ‘Better Times Will Come’ by No Luck Club off their album Prosperity
Filler Music: ‘Eclippse’ by Radical Face off his album Sunn Moonn Eclippse. Check out the video in the album link, it’s amazing.
Outro Music: ‘Fields of Russia’ by Mutefish off their album On Draught
