Podcaster: Morgan Rehnberg

Title:   Monthly News Roundup – A Golden Opportunity

Link :

S/2004 N1:
Exoplanet color:
Mars’ atmosphere:
Origin of Gold:

Description: In this episode of the Monthly News Roundup, Neptune gets a new friend and an exoplanet gets a color.  Curiosity finds new evidence about the fate of the martian atmosphere and a possible new origin for our planet’s gold is proposed.

Bio: Morgan Rehnberg is a graduate student in astrophysics and planetary science at the University of Colorado – Boulder.  When not studying the rings of Saturn, he develops software to help search for asteroids that might hit the Earth.  He blogs and podcasts about astronomy and space science at

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2013, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at



You’re listening to the 365 Days of Astronomy podcast for July 28th, 2013.  I’m Morgan Rehnberg and this is the Monthly News Roundup.  This episode was produced by Cosmic Chatter and recorded July 19th from Boulder, Colorado.


Let’s start this month with the remarkable discovery of a new moon of Neptune.  It’s not everyday that we find a new moon, and even rarer to find one from here at Earth.  Neptune’s new friend, provisionally named S/2004 N1, was discovered by SETI’s Mark Showalter in 150 images from the Hubble Space Telescope.

These images were actually taken years ago, starting in 2004, but no one noticed this tiny moon until now.  This turns out to not be that uncommon.  A small moon can often be dimmer than most of the stars in an image.  Without many consecutive images to show the moon’s motion, it’s nearly impossible to pick out.  Even if the moon’s motion is visible, you have to be looking for it, and there are usually other, more interesting, things in a given image.

Showalter is no stranger to this process, however.  S/2004 N1 brings his career total to six discovered moons and three discovered rings.  Among his other discoveries are the two recently-named moons of Pluto.

So what does this new moon look like? It’s small – only about ten kilometers across – and dark.  These combined to make it especially difficult to find from Earth.  Although it’s almost certainly not the last moon we’ll discover, it may be one of the last to be found from Earth. Smaller, dimmer moons can only be found by orbiting spacecraft.  And a spacecraft to Neptune is likely decades away at best.


From the red of Mars to the blue of Neptune, the planets in our solar system display a beautiful array of colors.  But what about the new, extra-solar planets being discovered by the bucket-load?  We expect them to be just as colorful, but, until now, this basic detail has remained un-obtainable.  For the first time, astronomers have observed the color of a planet outside our solar system.  The planet, HD 189733b, is a lovely cobalt blue.

Why is it so difficult to see something as fundamental as color?  The most common problem lies with how these planets are detected.  Many exoplanets are detected using the transit method, where a passing planet slightly dims the star.  With this technique, nearly all measured light comes from the star.  When the planet is not in front of the star, however, a tiny bit of light bounces off the planet’s surface and towards Earth.  This is the same effect that generates moonlight.

By making careful measurements with the Hubble Space Telescope, a team of astronomers were able to determine that the star appeared a little less blue when no light was being reflected.  This implied that HD 189733b must have a deep blue color.

Despite its color, this planet likely has more in common with Jupiter than Earth.  A so-called Hot Jupiter, it orbits extremely close to its star and sports a surface temperature of over a thousand degrees.

Color is closely linked with the chemical makeup of a body, so the more planet colors we can measure, the better we can understand what they’re made of and, ultimately, how they formed.


Mtars probably once had a thick atmosphere like the Earth does today.  Presently, however, the martian atmosphere is a mere one percent as thick as the Earth’s.  The question is – has the atmosphere been slowly leaking away over billions of years or did it vanish over a relatively short period?  New data collected by the Curiosity rover seems to support the latter idea

There are a number of ways for an atmosphere to disappear.  It can be absorbed by material on the surface, like oxygen depositing to form rust.  Light elements like hydrogen and helium simply float away if the planet it too small.  And, in the absence of a magnetic field, the solar wind can strip away material over time.

Some of the first detailed measurements of the martian atmosphere were made by the Viking mission in the 1970s.  Two landers and two orbiters studied the surface and atmosphere of the red planet, forming the basis for our knowledge of Mars today.  With newer technology, Curiosity is able to reproduce many of these observations with much increased accuracy.  Perhaps the most basic of these measurements is an analysis of which gases are present in the atmosphere today.

We can then compare those ratios to similar measurements of gas extracted from martian meteorites.  We know the approximate age of these rocks through other techniques, so we can create a sort of timeline of the atmosphere of Mars.  When compared to the atmosphere of today, it turns out that little has changed over the last several billion years – not a good sign for those hoping to find life.

Where’d the atmosphere go and is that process ongoing?  Curiosity will undoubtedly continue to consider these questions and more help is on the way.  Due to launch this November is MAVEN, NASA’s next Mars orbiter.  It’s expressly designed to study the composition and evolution of the martian atmosphere.  Ultimately, though, there will always be some ambiguity about an event that appears to have happened billions of years ago.


For millennia, gold has been the most precious of Earth metals.  Sought after in nearly every culture, it’s soft sheen continues to entice us today.  But, where did all the gold come from?

Conventional wisdom would tell you that it came from supernovae – giant explosions that mark the end of a star’s life.  Back at the time of the Big Bang, the Universe was basically nothing but hydrogen, the simplest element.  Over time, stars turn this hydrogen into heavier elements like carbon, nitrogen, oxygen… all the way up to iron.  After iron, however, there’s not enough energy to go on.  It’s not until the tremendous supernova explosion that heavier elements are formed.

New research, however, suggests that there may be another source for heavy elements like gold.  Instead of using the energy of a supernova, these elements can be created during the collision of two neutron stars.  Second only to black holes in density, colliding neutron stars carry an enormous amount of kinetic energy.  It might seem absurdly unlikely for two stars to collide, but it actually isn’t.  As many as half the stars in our galaxy are actually binary – meaning they orbit another star.           Over time, these orbits can degrade, leading to an inevitable collision.

It wouldn’t take a lot of collisions to produce a large amount of gold: one such event produces up to ten times the mass of our moon in gold – that’s quite the investment!


Thanks for listening to this episode of the 365 Days of Astronomy podcast.  For more astronomy news and commentary, visit or follow cosmic_chatter on Twitter.  As always, you can send your comments and corrections of  See you in August!


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365 Days of Astronomy
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