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Spec Tech: Weird Places in the Universe

July 21, 2011

Fictional universes can be strange places, but to my endless fascination the real universe — the one you and I actually live in — is a pretty strange place too. Over countless years of looking up astronomers have discovered some very, very strange things in the sky. Here are some odd places that really exist.

Trojan Asteroids

Trojan Asteroids refer to a group of asteroids that orbit ahead and behind Jupiter, but at the same distance from the sun and in lock step with the planet. This happens because there are semi-stable spots in orbital systems called Lagrangian points.

There are in fact hundreds of asteroids in our solar system. But the idea could work in any number of systems. The stability depends mainly on the ratio of masses of the two main orbiting bodies. There are probably not ‘Trojan planets’ around binary stars — at least similarly massed stars. But you could place any number of small rocks, or orbiting outposts at Lagrangian points of planets and moons or similar orbiting analogue.

Hypervelocity Stars

Hypervelocity stars need to be in this list because of their name alone. They’re actually normal stars, except for the fact that they are moving very fast with respect to the galaxy they inhabit – upwards of 2 million miles per hour! Discovered fairly recently, scientists are still figuring out exactly how they got going so fast. Most likely they are ejected from tight orbits with the massive black hole in the center of our galaxy.

hypervelocity stars

Hypervelocity stars - credit NASA / STScI

Here you see images of the wake of passing hypervelocity stars. Normally the gas and dust (called interstellar medium, or ISM) is cold and dark, but when slammed into by the passing star and its gasses the ISM heats up to thousands of degrees and emits light.

Hot Jupiters

The first planet around a star other than the Sun was discovered in 1992. Since then hundreds more have been identified and NASA’s Kepler mission alone is likely to turn up another thousand. These planets are so far away that we know very little about them. We’re only able to pick up the tiniest bit of light from them, just barely enough to know they exist. One of the big surprises is that many of them are large and massive, yet also very close to their host stars.

Traditional planetary formation theory (which isn’t very good yet) assumed that big planets like Jupiter could only form further out in the solar system where it is cool enough and the Sun’s energetic winds wouldn’t blow away all the gas and dust. In our solar system the only planets close to the sun are small, dense, and rocky. Yet we have found many large planets around other suns that orbit even closer than Mercury does here. Imagine a huge gas planet a hundred times the size of Earth orbiting its star once per week and heated to thousands of degrees!

Colliding Galaxies

Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. And yet there are so many galaxies around that eventually a couple of them collide.

The Antennae Galaxies - a pair of colliding galaxies

The Antennae Galaxies - a pair of colliding galaxies. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration

What does it mean for galaxies to collide though? They’re actually mostly empty space, with each star separated by tens of light years and the merger can take hundreds of millions of years. Rather than colliding like we think of solid objects doing they pass through each other — mostly. The exception is the interstellar medium. As the ISM of each galaxy slams together it heats up and groups into massive emission nebulae that form millions of big hot new stars. Notice how the in the image the colliding galaxies contain huge amounts of pink nebulae (stellar nurseries) and blue stars (massive hot young stars formed since the galaxies started colliding).

Binary Stars

It turns out that we’re a little weird. We only have one sun. Most of the stars in the Galaxy come in pairs. It’s even possible for there to be planets in stable non-lethal orbits around one or both of the stars in a binary system. We know much less about planetary formation around binary star systems, but we have found some planets in binary systems.

There is a great amount of diversity in binary star systems. Some of the stars are in tight circular orbits — so close they touch and exchange material. Others are distant and highly elliptical. Sometimes the stars are similar in size and temperature and sometimes they’re very different. Occasionally one of them burns out and collapses into a white dwarf while the other continues on. Almost every combination of hot/cold old/new close/far can be found.

Neutron Stars – Pulsars and Magnetars

Neutron Stars and one step removed from black holes. In fact the only thing that keeps them from collapsing any further is the quantum mechanical properties of neutrons; hence the name. As stars collapse they spin up faster and faster — like ice skaters when they pull their arms in. So neutron stars tend to be spinning very fast. Some of them emit radio waves like a lighthouse, sweeping across the cosmos. We see these radio beacons as flashing in a regular pattern here on Earth and named them pulsars.

Some neutron stars have been found to have enormous magnetic fields and we’ve taken to calling them magnetars. To put the magnetic field in perspective consider the magnetic field of the Earth. It’s pretty weak, but can point a compass in the right direction if there is sufficiently little friction on the magnetized needle. This field is about 30-60 microteslas, or 0.00006 tesla. A really strong magnet that you could hold in your hand might have a field as strong as 1 tesla. But magnetars have a magnetic field of 10 gigatesla: 10,000,000,000 tesla. It’s strong enough to kill a human from 1000 km away. Or blank a credit card from 200,000 km. Not objects you want to be close to.

Black Holes

Well this list wouldn’t be complete without mention of black holes: everyone’s favorite sci fi-but-real space object. Much has been written about them so I wont say too much. But they do have an interesting property that lets them go by different names. As material falls into a black hole it heats up and speeds up. As is speeds (and spins) up it flattens into a disk around the black hole. Some of this material get ejected at near the speed of light from the top and bottom of the disk forming astrophysical jets. These jets can be very bright across the electromagnetic spectrum turning up in all kinds of astronomical surveys. When the large black holes in the center of galaxies light up they are called active galactic nuclei (AGNs). Really bright AGNs in the early universe were so bright that we can see them from 12 billion light years away, near the edge of the visible universe. We call those Quasars.

The best part is we are still discovering new things. We are a curious species, always looking up and always building new telescopes. With such a large and interesting universe we have plenty of room to stretch our imaginations.

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