Einstein’s Final Riddle

Why does the Universe expand the way it does? Why does it accelerate? Einstein’s equations offer an explanation of gravity that works on the scale we know, but do they work on the grandest scales of space and time? Humanity now has a way to find out. The General Theory of Relativity predicts the behaviour of gravity, and includes a term known as the cosmological constant.  Einstein added this term to make the universe static and unchanging, as he believed it was.  But when the expansion of the universe was discovered by Edwin Hubble, Einstein regarded it as ‘the greatest blunder...

A Direct Black Hole

How did supermassive black holes form in the early epochs of the universe? More importantly, how did they have enough time to grow as large as they did? The answer requires a very different universe.  And back then, conditions were much different than they are now.  There was a lot of gas, little dust, no stars, and a plethora of dark matter. Astronomers have spent decades observing early quasars, massive active galaxies powered by huge black holes feeding on surrounding gas.  But these galaxies are seen so early in the universe’s history, one starts to wonder how a black hole finds sufficient...

Seeding The Supermassive

In the early Universe, things were quite different.  The first stars were much more massive than stars today, and contained mostly Hydrogen.  Astronomers have good ideas about how they formed, but other objects from around this time, namely black holes, are much tougher to account for.  Early black holes were huge, with no explanation for how they grew so large.  “Early” means “first Billion years after the Big Bang,” but even in that time, it’s hard to determine how observed black holes could grow as large as 100,000 solar masses. I say 100,000 solar masses, because that is the mass of two ‘seed’ black holes, discovered...

Mars in the Spotlight

On May 22nd, Mars will be at opposition.  It’s the astronomical term for when Mars and the Sun are on opposite sides of the Earth.  This makes the face of Mars fully illuminated from Earth, and also brings the Earth to it’s closest approach of Mars, at 75 Million Km.  Hubble images the red planet to celebrate the occasion. So get your telescopes out and be ready to take some pictures, because Mars is smiling! Mars will rise in the East at sunset, since they are on opposite sides of the Earth.  It will appear bright with a rusty hue, and...

Makemake Moon

Hubble just discovered the newest moon in the solar system, a tiny rock orbiting the dwarf planet Makemake, far beyond the orbit of Neptune. The new moon is about 250 Km across, compared to the 1,400 Km wide Makemake.  It orbits in approximately 12 days, and has an edge on orbit, making it difficult to spot. “Our preliminary estimates show that the moon’s orbit seems to be edge-on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake,” said Alex Parker of...

Hubble Bubble

Not to be confused with Canadian Gum Hubba-Bubba, Hubble has released a great birthday image for it’s 26th birthday.  I’m a few days late to celebrate, but it’s still a beautiful image. Known as NGC 7653, the Bubble nebula is 8,000 light years distant in the constellation of Cassiopeia.  The reason for this natural bubble shape is that the star just left of center in the image is ionizing a surrounding cloud of Hydrogen with it’s powerful stellar wind.  As electrons and protons recombine at the edges of the bubble, they release an infrared photon that can be clearly seen...

A Ring of Fire

A direct consequence of Einstein’s theory of general relativity, and an observational way to prove it, is gravitational lensing.  It requires a powerful gravitational source to work, such as a galaxy or cluster of galaxies.  It works in a similar way to a lens of glass, where rays of light are bent toward a single source, increasing the brightness.  In this case, instead of glass, the bending of the rays is due to the curvature of space. Light rays coming from the source would otherwise miss Earth, but instead are bent toward us when there is a massive object in front of it.  It’s...

Journey to the Center

As I’ve said before, the most powerful, most energetic, most intense processes happen in the center.  The gravitational center of the Earth, the Sun, and the galaxy are all places where temperature, pressure, and interactions of matter and energy are pushed to their limits.  When you look up to the sky it’s easy to see the Milky Way (unless you live in an urban center).  Do you ever wonder where the middle of it is? Where that supermassive black hole lies? Astronomers know where it is, but you need infrared cameras to see it past the thick dust that blocks...

Dark Matter in a Galaxy Cluster

We know that galaxies like our Milky Way are far more massive than we can see.  The dark matter in the Milky Way makes up 90% of it’s total mass.  Another way of saying this is the Mass to Light ratio, comparing the total mass inferred by the rotation speed of the galaxy to the total mass of stars in the galaxy.  This ratio, M/L, for the Milky Way, is about 10.  But for a galaxy cluster, the M/L ratio is more like 100.  Galaxy clusters are not just dense collections of stars and massive galaxies, they are also immense...