Philip Plait's Blog, page 18

Earth's solid inner core may be a little bit mushy

I know that I usually write about stuff you have to look up to see, but I also like to learn about what's going on under my feet. I'm biased; like most of you I live on a planet.

So I was fascinated to read that new findings imply that the Earth's inner core may not be entirely solid, and instead might have a mushy layer up to 250 kilometers deep in its upper reaches, and there could be both solid and liquid bits mixed in that layer as well.

OK, let's back up a bit. The Earth is not just a sol...

Tiny grains of alien material in meteorites point to origins in other stars

You are made of star stuff.

Carl Sagan said this in his series Cosmos, and it’s literally true. We know the early Universe only had hydrogen and helium (and a soupçon of lithium) in it, and all the heavier elements — carbon, oxygen, phosphorus, and more — were made in stars. These were then ejected into space, eventually making their way into you (some steps may have been skipped here for brevity).

We’ve known for a while that these elements were created in many different stars. The Sun formed...

Asteroids, the Universe, and Everything: Meet 42 space rocks

Between Mars and Jupiter in our solar system lies the Main Asteroid Belt, a region over 150 million kilometers across where most of the biggest asteroids lie. The first, Ceres, was discovered on January 1, 1801, and since then over a million more have been found. There may be a billion or more larger than 100 meters in size.

Because they’re far away and tend to be small, they appear as dots in telescopes — the name "asteroid" means "star-like." That’s been true for decades, centuries really, un...

Astronomers find 17 red dwarf stars that may have aurorae triggered by orbiting Earth-sized planets

Following up on work presented last year with a single star, a team of astronomers has found evidence for planets orbiting quite a few nearby red dwarf stars, and they’ve done it in an entirely new way: By looking for aurorae on the stars themselves.

An aurora on Earth is caused when electrically charged subatomic particle (like electrons) in the Sun’s solar wind stream past the Earth and are caught by our planet’s magnetic field. The mechanism is pretty complex but in a nutshell these particle...

G1.9+0.3: The last galactic supernova

When was the last supernova in our galaxy?

This questions sounds straightforward but it’s actually a little bit convoluted to answer. But just a little, so sit back and let’s talk about a science communication mistake, light travel time, and what happens when an entire star explodes. Sometimes two.

So. I recently wrote about a stellar explosion 900 years ago called Supernova 1181, and how astronomers have finally identified the expanding debris from that catastrophic event.

When I wrote about...

This lopsided galaxy is a mess. But why?

In astronomy, like with most fields of science, there are mysteries we run across we can’t explain. In movies and TV show this usually means some extremely weird phenomenon that’s about to fall from the sky or break out of a beaker and wreak havoc, and the scientist in the story has no idea why.

In real life though the mystery is usually a little less life-threatening and more of a “Huh. I wonder what’s going on here?” kind of a thing. And the problem isn’t that we don’t have an explanation, it...

We got to Pluto just in time: Its air is starting to freeze out

The New Horizons mission to the outer solar system flew past Pluto in July 2015, skimming over its surface by just 12,500 kilometers after a journey of 5 billion kilometers and returning incredible images and data of the tiny, icy world.

The mission was conceived, designed, built, and launched in record time because scientists wanted to get to Pluto as rapidly as possible. Why? Because Pluto orbits the Sun on a decently elliptical path, and around the year 1989 it was its closest point to the S...

WASP-76b is hot enough to ionize your bones

One of the most amazing things we’ve learned by discovering exoplanets — alien worlds orbiting other stars — is just how humdrum our own solar system is.

The very first planets confirmed orbited a pulsar, the animated corpse of a massive star that had exploded long ago in a supernova. The first planets found orbiting “normal” stars like the Sun were hot Jupiters: massive gas giants like our own, but orbiting so close to their host stars they’re hotter than Mercury.

Among those, WASP-76b a scor...

Take THAT Tatooine: A planet may be orbiting a *triple* star system

In a possible exoplanetary first, astronomers have presented evidence of a planet orbiting around all three stars in a trinary star system. If true the planet would likely be massive, and revealed itself via its gravity torqueing a huge disk of gas and dust surrounding the stars, and carving a deep gap in it as well.

The star system is called GW Orionis (or just GW Ori), about 1,300 light years from Earth. It’s what’s called a hierarchical trinary, meaning it has two stars orbiting each other i...

BepiColombo's first kiss with Mercury!

Over the weekend (on October 1), the joint European/Japanese Space Agencies spacecraft BepiColombo passed Mercury for the first time, skimming just 199 kilometers above the planet’s surface!

That’s a seriously close shave, but it was over Mercury’s nightside so no images were taken. Not long after, though, when it was 2418 km away, it took this extremely cool shot of innermost planet:

Ten minutes after closest approach to Mercury on October 1, 2021, BepiColombo took this image (left) of the pl...