Mind the Gap

My latest at Sky and Telescope

One Gap, No Planets

Where’s the planet that should be to blame for this star’s carved-out disk?

This illustration shows a young star with its dusty disk, in which a gap has been carved out. Astronomers think such gaps signal the formation of planets.

 

How do planets form? This deceptively simple question has sparked a new field in astronomy over the last two decades. Astronomers have used telescopes all over the world (and in orbit!) to study all stages of planet formation, from disks of material around infant stars to the scattered debris and planetesimals in systems such as Fomalhaut’s. The goal of all these studies is the development of a coherent scenario that explains the behavior and evolution of planet-forming disks around young stars and links them to the exoplanets observed around older stars (such as those glimpsed by Kepler).

Click here to read the whole article.

A Stellar Senior Citizen

Here’s my latest at Sky and Telescope:

“The search for the oldest stars in the Universe has just turned up a new candidate: HD 140283. This 7th-magnitude sub-giant has intrigued astronomers for decades. It was one of the first stars found with an extremely low concentration of heavy elements in its outer atmosphere, compared with the Sun. And this composition makes the star — which has roughly the same temperature as the Sun — look like a star twice as hot as it is. 

Now, Howard Bond (Space Telescope Science Institute and Penn State) and his colleagues have confirmed that HD 140283 may be one of the first stars born after the Big Bang, they report in the March 1st Astrophysical Journal Letters.”

Site News

Hi All

I haven’t updated this page in a while, but I have been busy blogging at Sky & Telescope.  For the time being, I will link my new posts from that site here, until I can find a more suitable solution.

 

Here are the latest articles:

Four Mammoth Cameras Take on the Sky

Auroras Grace Stellar Skies

A New Goldilocks Planet

Making Mini-Oort Clouds

 

The First Stars in the Universe

Star formation is one of the great unsolved problems in astronomy.  It is very difficult to simulate the star formation process with a computer mainly because it is a problem that spans many orders of magnitude in size, temperature and pressure, and must incorporate a variety of chemical processes. More simply put, there are hardly any spots to make approximations.  But solving star formation is still very important, because without stars, you wouldn’t be sitting here reading this blog today.  When massive stars explode (or supernova) they seed the space around them with heavy elements, such as the iron in your blood.  These explosions also help future generations of stars form.  Understanding how star formation works today keeps a lot of astronomers (both theorists and observers) very busy, but some astronomers like a challenge.  These astronomers study the first stars to ever form.

Squishing a Neutron Star

The final end products of stars are really extreme. Stars like the Sun end up as “white dwarfs”, where the exposed core of the former star is left behind, and about 60% of the total mass of the star is jammed into something the size of the Earth. A spoonful of a white dwarf would weigh about 1 ton (here on earth). Stars much more massive than the Sun end their lives as black holes. Good luck getting a black hole on a spoon. Its gravitational force would be so intense, the molecules that compose the spoon, your hand, and your arm would be shredded apart. In between black holes and white dwarfs are objects called neutron stars. They are much more dense than white dwarfs. One spoonful of a neutron star would weigh about 1 billion tons. Which raises some interesting questions.

Tiny Particles, Big Equations

Sorry for the delay. I’ve been busy and neglecting my blogging duties. -John

Astronomy basically proceeds in one of two ways. Observers (like me) go out and use telescopes to record positions and brightnesses on the sky. We take that data and compare to models that theorists produce that allow us to infer what is going on at the source of the light that we record. In a paper titled “Neutrino Spectra from Accretion Disks: Neutrino General Relativistic Effects and the Consequences for Nucleosynthesis” by O.L Caballero, G.C. McLaughlin and R. Surman, the authors make theoretical predictions for the behavior of protons, neutrons and neutrinos in the accretion disks around black holes.

The Universe’s Biggest Explosions

Everyday, there are a few explosions ripping through distant galaxies that produce enough energy in a few seconds to power the Sun for its entire lifetime. Or in more terrestrial terms, these explosions are as powerful as 10,000,000,000,000,000,000,000,000,000,000,000,000 100 watt lightbulbs. Yet, no one knew about them until the 60s. Even then, they weren’t detected by astronomers, but by U.S. satellites designed to sniff out Soviet nuclear testing. It wasn’t until the late 90′s that they were studied in large numbers. Now, with data coming from the Swift satellite, astronomers have started to more fully understand what may be causing these large explosions.