Philip Plait's Blog, page 32

Hey Mars, what's shakin'?

NASA's Mars InSight lander just detected two more relatively large quakes on the Red Planet, and they came from the direction of a very interesting region that is known to be tectonically active. This highlights one of the bigger questions we have about Mars: Is it volcanically active today? Like, now?

InSight touched down on in a volcanic plain called Elysium Planitia on November 26, 2018. Its main mission is to study the interior of Mars using seismographs, a heat probe, and radio signals to ...

Terrascope: The Whole Earth Telescope

One of the biggest problems is astronomy is a simple one: Not enough light. One of the reasons we make telescopes so big is to collect light to see faint things. The analogy is like a bucket in rain: The wider the bucket the more rain you collect. Photons fall from the sky, and the bigger your mirror the more light you collect.

It's hard to make big telescopes. Supporting a mirror bigger than 8 meters is hard, though making them segmented (like the James Webb Space Telescope) helps. Still, the ...

The interstellar comet Borisov was shiny and new when it passed through our solar system

For a long time, astronomers thought our second alien interstellar visitor*, the comet 2/I Borisov, was rather boring: It looked pretty much like every small comet from our own solar system.

However, now it appears that it was special: It was pristine, almost completely unchanged since it formed, meaning ours was the first solar system it visited closely.

Isn't that nice?

Hubble Space Telescope image of the comet 2I/Borisov (formerly C/2019 Q4 (Borisov)). The blue color was added to a graysca...

The birth of a little black hole may have revealed a much bigger black hole

The birth cry of a distant black hole may have revealed the existence of a closer, much more massive black hole, part of a population of these beasts that is proving devilishly difficult to find.

There are three general classes of black holes we know of. One is created when a massive star explodes, or two superdense neutron stars collide. These tend to have between roughly 5 and 50 times the mass of the Sun, so we call them stellar-mass black holes.

Supermassive black holes are the second kind...

Meet G117-B15A: the most stable optical clock in the Universe

Not too far away in galactic terms — 187 light years from us — is the remains of a dead star. It was once like the Sun, though perhaps six or so times more massive, and 400 million years ago it reached the end of its mainstream life. It swelled into a red giant, cast off its outer layers, and eventually lost so much material it exposed its hot, dense core to space.

This kind of object is known as a white dwarf, and is the end state for some 90% of all stars in the sky. But this particular one, ...

Mars may be sneezing out dust into the solar system that’s visible from Earth

If you go outside at night in a dark spot with no moonlight, you may spot a faint glow in the sky that follows the zodiac constellations. This glow is called the zodiacal (zo-DIE-uh-cull) light, and is caused by tiny particles of dust orbiting the Sun outside Earth’s orbit. They faintly reflect sunlight back to us, generally barely visible by eye though obvious enough in photos.

What’s not obvious is the source of that dust. It was once thought to be from asteroids; big rocks in the main astero...

Was Earth once a water world?

Was the Earth's surface once inundated with water?

Clever new research combining physical models with experiments adds to the growing evidence that billions of years ago the Earth was a water world, covered in twice as much water as it has on the surface now, possibly submerging even the highest peaks.

It's not proof, but things really are starting to line up that this is the case.

The mystery here lies in the Earth's mantle. This is the layer of extremely hot (but not molten!) rock under the...

Event Horizon Telescope sees the magnetic engine behind a supermassive black hole's immense power

In 2019, astronomers stunned the world, releasing an epic image of material swirling around the supermassive black hole in the core of the galaxy M87 55 million light years from Earth. They connected radio telescopes from around the planet to create the Event Horizon Telescope, a virtual telescope mimicking the power of a telescope the size of our planet, to achieve this amazing observation.

More observations also showed the material around the black hole changed in brightness, even as the ring...

A planet for Vega?

Vega is arguably one of the prettiest stars in the night sky. Brilliant and blue, it's the sparkling sapphire that marks the constellation Lyra high in the northern sky. It's one of the brightest stars in the sky, due to it being close to us, just 25 light years away, and intrinsically luminous, pouring out 40 times more energy than the Sun.

And a paper that's just come out indicates it might — might — have a planet orbiting it. If so, that's pretty interesting, and not just because we can send...

Full metal volcano

We're all familiar with what volcanoes are like on Earth. They come in different sizes and shapes, and eruptions can be different — some are explosive, some have arcing fountains, some just ooze out slowly — but they all have one thing in common: The lava is made of molten rock.

Earth has a thin, solid rocky crust over a very thick mantle, made of extremely hot (but not molten!) rock. Sometimes the mantle near the crust does melt, and this material rises and breaks through, causing volcanic eru...