One of the biggest challenges to measuring the expansion of the universe is the fact that many of the methods we use are model-dependent. The most famous example is the use of distant supernovae, where we compare the standard brightness of a Type Ia supernova with their apparent brightness to find their distance. But knowing the standard brightness depends upon comparing them to the brightness of Cepheid variables which is in turn determined by measuring the distances of nearby stars via parallax. Every step of this cosmic distance ladder depends upon the step before it.Continue reading “A new Technique Could use Quasars to Directly Measure the Expansion Rate of the Universe”
One of the strangest predictions of general relativity is that gravity can deflect the path of light. The effect was first observed by Arthur Eddington in 1919. While the bending effect of the Sun is small, near a black hole light deflection can be significant. So significant that you need a powerful supercomputer to calculate how light will behave.Continue reading “You Thought Black Hole Event Horizons Looked Strange. Check out Binary Black Hole Event Horizons”
In 1915, Einstein put the finishing touches on his Theory of General Relativity (GR), a revolutionary new hypothesis that described gravity as a geometric property of space and time. This theory remains the accepted description of gravitation in modern physics and predicts that massive objects (like galaxies and galaxy clusters) bend the very fabric of spacetime.
As result, massive objects (like galaxies and galaxy clusters) can act as a lens that will deflect and magnify light coming from more distant objects. This effect is known as “gravitational lensing,” and can result in all kinds of visual phenomena – not the least of which is known as an “Einstein Cross.” Using data from the ESA’s Gaia Observatory, a team of researchers announced the discovery of 12 new Einstein Crosses.Continue reading “Gaia Finds 12 Examples of Einstein Crosses; Galaxies Being Gravitationally Lensed so we see Them Repeated 4 Times”
Black holes come in three sizes: small, medium, and large. Small black holes are of stellar mass. They form when a large star collapses at the end of its life. Large black holes lurk in the centers of galaxies and are millions or billions of solar masses. Middle-sized black holes are those between 100 to 100,000 solar masses. They are known as Intermediate Mass Black Holes (IMBHs), and they are the kind we least understand.Continue reading “An Intermediate-Mass Black Hole Discovered Through the Gravitational Lensing of a Gamma-ray Burst”
It’s relatively rare for a magical object from fantasy stories to have a analog in real life. A truly functional crystal ball (or palantir) would be useful for everything from military operations to checking up on grandma. While nothing exists to be able to observe the mundanities of everyday life, there is something equivalent for extraordinarily far away galaxies: gravitational lenses. Now a team led by Xiaosheng Huang from Lawrence Berkeley National Laboratory (LBNL) and several universities around the world have published a list of more than 1200 new gravitational lensing candidates.Continue reading “Dark Energy Survey Finds Hundreds of New Gravitational Lenses”
A very rare astronomical phenomenon has been in the headlines a lot recently, and for good reason. It will be hundreds of years until we can see Jupiter and Saturn this close to one another again. However, there are some even more “truly strange and very rare phenomena” that can currently be observed in our night sky. The only problem is that in order to observe this phenomena, you’ll need access to Hubble.Continue reading “One of the Largest, Most Complete Einstein Rings Ever Seen. Astronomers Call it the “Molten Ring””
As Einstein originally predicted with his General Theory of Relativity, gravity alters the curvature of spacetime. As a consequence, the passage of light changes as it encounters a gravitational field, which is how General Relativity was confirmed! For decades, astronomers have taken advantage of this to conduct Gravitational Lensing (GL) – where a distant source is focused and amplified by a massive object in the foreground.
In a recent study, two theoretical physicists argue that the Sun could be used in the same way to create a Solar Gravitational Lens (SGL). This powerful telescope, they argue, would provide enough light amplification to allow for Direct Imaging studies of nearby exoplanets. This could allow astronomers to determine if planets like Proxima b are potentially-habitable long before we send missions to study them.Continue reading “If We Used the Sun as a Gravitational Lens Telescope, This is What a Planet at Proxima Centauri Would Look Like”
Astronomers have to be extra clever to map out the invisible dark matter in the universe. Recently, a team of researchers have improved an existing technique, making it up to ten times better at seeing in the dark.Continue reading “A new way to map out dark matter is 10 times more precise than the previous-best method”
It now seems clear that dark matter interacts more than just gravitationally. Earlier studies have hinted at this, and a new study supports the idea even further. What’s interesting about this latest work is that it studies dark matter interactions through entropy.Continue reading “Something other than just gravity is contributing to the shape of dark matter halos”
Gravity is a strange thing. In our everyday lives, we think of it as a force. It pulls us to the Earth and holds planets in orbits around their stars. But gravity isn’t a force. It is a warping of space and time that bends the trajectory of objects. Throw a ball in deep space, and it moves in a straight line following Newton’s First Law of Motion. Throw the same ball near the Earth’s surface, and it follows a parabolic trajectory caused by Earth’s warping of spacetime around it.Continue reading “Gravitational-Wave Lensing is Possible, but it’s Going to be Incredibly Difficult to Detect”