Date: November 7, 2011

Title: Dirty Snowballs & Giant Planets: X-ray Secrets of our Solar System Revealed

Organization: The Chandra Telescope Team

Link: www.chandra.si.edu

Description: Just in time for the Year of the Solar System, the Chandra X-ray Telescope takes a look at some of the objects in our Solar System, from comets to the largest planets, through it’s X-ray eyes.

Bio: NASA’s Chandra X-ray Observatory is a telescope specially designed to detect X-ray emission from very hot regions of the Universe such as exploded stars, clusters of galaxies, and matter around black holes. Because X-rays are absorbed by Earth’s atmosphere, Chandra must orbit above it, up to an altitude of 139,000 km (86,500 mi) in space. The Smithsonian’s Astrophysical Observatory in Cambridge, MA, hosts the Chandra X-ray Center which operates the satellite, processes the data, and distributes it to scientists around the world for analysis. The Center maintains an extensive public web site about the science results and an education program.

Transcript:

Dirty Snowballs & Giant Planets: X-ray Secrets of our Solar System Revealed

Narrator: The Solar System is our cosmic home. The Sun, Moon, planets, comets, and asteroids are all our neighbors. Many objects in the Solar System are visible with the unaided eye, such as the Sun on a clear day, the Moon during the night, and many planets, and then the occasional comet.

But what happens when you look at the Solar System through a new set of eyes? That’s what astronomers have been learning since they have been using the Chandra X-ray Observatory to study objects within our own Solar System. Chandra can see what happens when radiation from the Sun interacts with the colder objects in our Solar System like planets, comets, and even our own Earth and Moon.

Dr. Scott Wolk of the Chandra X-ray Center has been involved with Chandra observations of objects in our Solar System. In particular, Scott has been involved with many observations of comets, which have turned out to be fascinating objects to study in X-rays.

Scott: Probably the most surprising objects observed in X-rays are comets. Now X- rays are normally associated with the hottest things in the universe, black holes, the beginning of the universe… Comets were pretty well described by Fred Whipple as being “dirty snowballs”. So how does a snowball make X-rays? It gets back to a strange phenomenon called charge exchange. The Sun is constantly streaming very hot particles called ions into the Solar system. This stream is called the solar wind, and the ions are so highly charged that they will actually steal electrons from cold gas if they can. A comet becomes active when it gets close to the Sun and it starts putting cold gas out into space, and as you can imagine, it is quite cold. This charge exchange takes place every time an ion gets close to a cold gas molecule, and each time this happens, an X-ray is emitted. This makes comets very bright in X-rays. Comets are so bright that some scientists think we will be able to see comets around other stars in X-rays, and this could become a very powerful way to find planet systems around stars which are not suitable for the current method.

We have looked at something like 8 comets so far, and they all look different. We are learning how much gas leaves the comet each time it passes in front of the sun, what the “snow” inside of the comet is really made of. We observed the collision of Deep Impact into the comet Temple 1 on the 4th of July, 2005 and could actually see the jet of material freed from the comet by that impact flying off into space.

Narrator: Chandra has made observations of individual comets so far, but thats not the end of the story. In fact astronomers hope that they can use X-ray observations of comets as probes into the solar wind throughout the solar system.

Scott: Not only do the comets tell us about themselves, they also tell us about the solar wind that theyre traveling through and what it is made of and how fast it is going. This is sometimes called space weather. Now, bad space weather can be a pretty bad thing. It can interrupt communications on Earth. It can actually interrupt electrical power on Earth, and it can be very dangerous to satellites and astronauts. The space station even has a special room just in case of bad space weather, and NOAA, which is responsible for hurricane forecasts on Earth, also has satellites to help predict space weather. Most satellites are very close to the Earth and don’t tell us a lot about what the space weather is like in different parts of the solar system. So this is a lot like living in Boston and trying to predict the weather without knowing much about the weather in Chicago. Comets on the other hand are all over the place and give us occasional space weather reports from all over the solar system and these give us a better idea about how the space weather differs from place to place in our solar system. And this will be very important when Astronauts move further out into space.

Narrator: Jupiter and Saturn are the two largest planets in our Solar System, best known for very different reasons. Most people think of Jupiter’s famous Great Red Spot, while Saturn is, of course, most loved for those excellent rings. These two planets, however, offer much, much more for astronomers looking to learn more about our Solar System.

Scientist: It’s hard to imagine x-rays coming from a planet. X-rays are a kind of light we associate with some of the hottest things in the universe, neutron stars, supernova remnants and black holes. If you were to find x-rays coming from a planet, you would think that all the planets would be the same, maybe reflecting x-rays from the Sun. But as we’ve already seen everywhere else in the universe, things are never that simple. In fact, the stories of Jupiter and Saturn, the two largest planets in the solar system, are completely different.

Narrator: Let’s take a look at Saturn first and find out what Chandra has told us so far.

Scientist: Saturn’s atmosphere does in fact act like a big massive fuzzy mirror, reflecting X-rays emitted by the Sun back to the Earth, much like it reflects sunlight back to us that we see in the night sky. How are we so certain about this? Well, the Sun flares in x-rays, getting hundreds of times brighter, and the Sun flared during one of the Chandra observations of Saturn. Two hours and 14 minutes later, exactly the amount of time it takes light to go to Saturn and back to Earth, we saw Saturn get brighter in x-rays. Now one can imagine in the future using Jupiter or Saturn to let us know if the far side of the sun flares. This could be important to astronauts traveling deep in the solar system.

Narrator: Astronomers were also able to take advantage of a rare alignment of Saturn’s moon, Titan. On January 5, 2003, Titan crossed in front of the Crab Nebula, which is a very strong X-ray source.

Scientist: Now because the Crab pulsar and the nebula is so bright in x-rays, we effectively got a good old-fashioned x-ray of Titan, just like you get when you go to the doctors office and they put a strong x-ray beam on one side and a film on the other side and your arm, your finger, or whatever you might have broken, in between. These data reveal elements high up in the atmosphere of one of the few bodies in the solar system that actually has liquid on its surface.

Narrator: Let’s return to Jupiter. Scott Wolk describes some of what Chandra has revealed about this gas giant planet.

Scientist: Jupiter can also reflect x-rays, just like Saturn, but it has a strong magnetic field which makes things a lot more interesting. Charged particles, possibly from the Sun in what’s called the solar wind, possibly from material sputtered off the moon Io, can get captured by the magnetic field of Jupiter and driven towards the million-volt environment above the planet’s poles. I say possibly because the region where the x-rays are seen on Jupiter is actually a little bit too close to the poles to be coming from either source directly and there’s some new astrophysics we need to learn.

Narrator: While we’ve sent spacecraft out to study the outer Solar System, certain secrets may only be revealed through the X-rays that Chandra can detect. Scientists will continue to use the observatory to unlock the mysteries of our planetary neighbors.

End of podcast:

365 Days of Astronomy
=====================
The 365 Days of Astronomy Podcast is produced by the Astrosphere New Media Association. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.