The Case of the “Missing Exoplanets”

An illustration of the variations among the more than 5,000 known exoplanets discovered since the 1990s. Credit: NASA/JPL-Caltech

Today, the number of confirmed exoplanets stands at 5,197 in 3,888 planetary systems, with another 8,992 candidates awaiting confirmation. The majority have been particularly massive planets, ranging from Jupiter and Neptune-sized gas giants, which have radii about 2.5 times that of Earth. Another statistically significant population has been rocky planets that measure about 1.4 Earth radii (aka. “Super-Earths”). This presents a mystery to astronomers, especially where the exoplanets discovered by the venerable Kepler Space Telescope are concerned.

Of the more than 2,600 planets Kepler discovered, there’s an apparent rarity of exoplanets with a radius of about 1.8 times that of Earth – which they refer to as the “radius valley.” A second mystery, known as “peas in a pod,” refers to neighboring planets of similar size found in hundreds of planetary systems with harmonious orbits. In a study led by the Cycles of Life-Essential Volatile Elements in Rocky Planets (CLEVER) project at Rice University, an international team of astrophysicists provide a new model that accounts for the interplay of forces acting on newborn planets that could explain these two mysteries.

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This is How You Get Moons. An Earth-Sized World Just got Pummeled by Something Huge.

An MIT-led team has discovered evidence of a giant impact in the nearby HD 17255 star system, in which an Earth-sized terrestrial planet and a smaller impactor likely collided at least 200,000 years ago, stripping off part of one planet’s atmosphere. Credits:Image: Mark A. Garlick

Titanic collisions are the norm in young solar systems. Earth’s Moon was the result of one of those collisions when the protoplanet Theia collided with Earth some 4.5 billion years ago. The collision, or series of collisions, created a swirling mass of ejecta that eventually coalesced into the Moon. It’s called the Giant Impact Hypothesis.

Astronomers think that collisions of this sort are a common part of planet formation in young solar systems, where things haven’t settled down into predictability. But seeing any of these collisions around other stars has proved difficult.

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A Black Hole or Neutron Star Fell Into Another Star and Triggered a Supernova

Artist's conception of the ring of material surrounding a star shortly after engulfing a dense companion. Credit: Bill Saxton, NRAO/AUI/NSF

What happens when you slam a neutron star (or black hole, take your pick) into a companion star? A supernova, that’s what. And for the first time ever, astronomers think they’ve spotted one.

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When Galaxies Collide, Black Holes Don’t Always Get the Feast They Were Hoping for

galaxies collide
This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth's night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. (Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger)

What happens when galaxies collide? Well, if any humans are around in about a billion years, they might find out. That’s when our Milky Way galaxy is scheduled to collide with our neighbour the Andromeda galaxy. That event will be an epic, titanic, collision. The supermassive black holes at the center of both galaxies will feast on new material and flare brightly as the collision brings more gas and dust within reach of their overwhelming gravitational pull. Where massive giant stars collide with each other, lighting up the skies and spraying deadly radiation everywhere. Right?

Maybe not. In fact, there might be no feasting at all, and hardly anything titanic about it.

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About 3% of Starlinks Have Failed So Far

Starlink
An artist's conception of Starlink in orbit. Credit: SpaceX

SpaceX has drawn plenty of praise and criticism with the creation of Starlink, a constellation that will one-day provide broadband internet access to the entire world. To date, the company has launched over 800 satellites and (as of this summer) is producing them at a rate of about 120 a month. There are even plans to have a constellation of 42,000 satellites in orbit before the decade is out.

However, there have been some problems along the way as well. Aside from the usual concerns about light pollution and Radio Frequency Interference (RFI), there is also the rate of failure these satellites have experienced. Specifically, about 3% of its satellites have proven to be unresponsive and are no longer maneuvering in orbit – which could prove hazardous to other satellites and spacecraft in orbit.

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Astronomers See the Wreckage from a Collision Between Exoplanets

RArtist’s concept illustrating a catastrophic collision between two rocky exoplanets in the planetary system BD +20 307, turning both into dusty debris. Credits: NASA/SOFIA/Lynette Cook

The history of our Solar System is punctuated with collisions. Collisions helped create the terrestrial planets and end the reign of the dinosaurs. And a massive collision between Earth and an ancient body named Theia likely created the Moon.

Now astronomers have found of evidence of a collision between two exoplanets in a distant solar system.

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Weekly Space Hangout – February 7, 2014: New Impact on Mars & A Wobbly Planet

Host: Fraser Cain
Astrojournalists: Scott Lewis, Nicole Gugliucci, Morgan Rehnberg, Brian Koberlein, Elizabeth Howell, Amy Shira Teitel, David Dickinson

This Week’s Stories!

Morgan Rehnberg (cosmicchatter.org / @cosmic_chatter):
New Mars impact crater

Nicole Gugliucci (cosmoquest.org / @noisyastronomer):
Weird Asteroid Itokawa Has a Dual Personality
Shiny new radio image of M82 (but no supernova afterglow)

David Dickinson (@astroguyz):
Venus in 2014
Progress+launches for February
Space History-Curious Artifacts Sent Into Space

Elizabeth Howell (@howellspace):
Astronomy Podcast Enters Sixth Year — And We’d Love For You To Contribute!
Super-Earths Could Be More ‘Superhabitable’ Than Planets Like Ours

Brian Koberlein (@briankoberlein); Scott Lewis (@baldastronomer); & Elizabeth Howell (@howellspace):
‘Wobbly’ Alien Planet Has Weird Seasons And Orbits Two Stars

Amy Shira Teitel (@astVintageSpace):
When galaxies collide!

Scott Lewis (@baldastronomer):
Gaia

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.