Philip Plait's Blog, page 23

Sometimes, galaxies collide

Sometimes, galaxies collide.

A statement simple in its structure, but breathtaking in its profundity.

This was something not understood until later in the 20th century. It wasn't until the 1920s or so that we even understood that galaxies were entities separate from the Milky Way, colossal structures of their own with billons of stars in them. When this was finally grasped, the size of the Universe jumped by orders of magnitude in human understanding.

They're immense, tens or hundreds of thou...

First a red giant cooks its planets, then it turns them into mini-stars

A long standing astronomical mystery may finally be solved. It involves dying stars, torched planets, rejuvenating those planets as kinda-sorta stars, and big ol' clouds of dust.

A lot of stars are what we call variable, meaning they change their brightness over time. Some are irregular, in that they just seem to get brighter and dimmer at random times (see Boyajian's Star), while others are regular or periodic variables, which get brighter and/or dimmer on regular cycles.

Almost all the reaso...

What is this cloud of gas bigger than a galaxy doing all by its lonesome?

Astronomers have found a truly gigantic and fiercely hot cloud of gas floating near the edge of a galaxy cluster, and it’s blasting out X-rays. Hot gas is common in clusters, but usually concentrated near the center and thinner the farther you go outward. This one is a singular cloud millions of light years off to the side, and also seems to have a source of energy gently exciting the gas that is nowhere to be seen.

Oh, I do so love the weird ones.

Clusters of galaxies are truly gigantic struc...

Is Saturn’s moon Dione still cryovolcanically active?

Every now and again, I am strongly reminded that the Universe is really weird.

We’re used to the way things go on Earth. We have air, the wind blows, most of the surface is water. And when we think of volcanic eruptions, we think of molten rock spewing up from the planet’s extremely hot interior.

But far away from the Earth and Sun there are bodies that are too cold and small to have molten rock. Heck, they hardly have any rock. Yet they too can be volcanic… except in their case it’s liquid wa...

A magnetar is outbursting again right on schedule

Magnetars are bizarre and terrifying objects, capable of immense explosions that are detectable hundreds of millions of light years away. We also don’t know that much about them.

A team of scientists, though, had their own flash of insight that provides another clue on how these tiny but mighty monsters work. They found a magnetar in our galaxy that has predictable periodic outbursts.

Kinda.

A rotating neutron star with a powerful magnetic field whips up subatomic particles around it. Artwork...

Psyche is the most metal asteroid: It may have volcanoes that spewed molten iron

I'm very excited about the Psyche mission. Due to launch next year, this NASA spacecraft will arrive at its target in the main asteroid belt four years later: The odd asteroid 16 Psyche.

Most asteroids are rocky, and some even have ice under their surface, but Psyche is an M-class asteroid, meaning it’s highly metallic (mostly iron and nickel). It’s big, over 200 kilometers across, and quite shiny — a typical asteroid reflects roughly 4% of the sunlight hitting it, but Psyche reflects 16%. Agai...

This is the best time all year to see the ringed magnificence of Saturn

On Sunday night, August 1, the incredible beauty that is Saturn will be the closest it gets to Earth all year.

At that time it will be about 1,336,700,000 kilometers from Earth. That's still a long way — space is big, hence its name — but the planet will look incredible and gorgeous even through a small telescope.

We call this event opposition, because Saturn is opposite the Sun in the sky. Another way to think of it is that Earth is directly between Saturn and the Sun, so our two planets are ...

Forecast for Jupiter's moon Ganymede: Extremely cold and… humid?

Using a combination of old and new data from Hubble Space Telescope, astronomers have found water vapor in the atmosphere of Jupiter’s planet-sized moon Ganymede!

This is very cool news, literally: On most of the moon it’s too cold for water vapor, but in some spots where it’s warmest they found the highest abundance of it, clearly indicating it’s coming from sunlight heating the surface. Plus, bizarrely, a contribution from Jupiter’s ridiculously fierce magnetic field.

Ganymede is the largest...

An ancient remnant of a galactic collision encircles the Sombrero Galaxy

Astronomers have found a huge ring structure looping around the nearby (and absolutely spectacular) galaxy M104, also known as the Sombrero Galaxy. It’s likely elliptical, encircling the entire galaxy and something like 370,000 light years along its long axis.

This ring is almost certainly made up of stars, and is what’s called a stellar stream, the remnants of a smaller galaxy eaten by a bigger one. It’s known that the Sombrero suffered a massive collision more than 3.5 billion years ago, but ...

Magnificent Hubble image of a cluster warping space and stripping gas

The Universe is filled with a lot of weird stuff, but one of the weirdest phenomena is gravitational lensing.

I've written about it before

Briefly, gravitational lensing is when the gravity of a massive object — a star, a black hole, a galaxy — bends space around it, causing light passing by to curve, like a car following the curve of a road. Einstein [wrote about this in relation to his work on Relativity], saying that matter bends space and we perceive this bending as gravity. So we call thi...