As the search continues for Earth-size planets orbiting at just the right distance from their star, a region termed the habitable zone, the number of potentially life-supporting planets grows. In two decades we have progressed from having no extrasolar planets to having too many to search. Narrowing the list of hopefuls requires looking at extrasolar planets in a new way.

But Tau Ceti already doesn't make the cut.

I am presently in Athens for a few days, to give a seminar and meet the local group of CMS physicists. So I took the chance to visit yesterday evening the Astrophysics department of the University of Athens, where at the top floor is housed a nice 40cm Cassegrain telescope (see picture below). There I joined a small crowd which professor Kosmas Gazeas entertained with views of Jupiter, the Moon, Venus, and a few other celestial targets. I need to thank my friend Nadia, a fellow physicist and amateur astronomer, for inviting us to the event.

What does it mean when a supermassive black hole exists in a place where it isn't supposed to exist? It's another puzzle of the early universe.

Henize 2-10 is a small irregular galaxy that is not too far away, at least in astronomical terms: 30 million light-years. "This is a dwarf starburst galaxy -- a small galaxy with regions of very rapid star formation -- about 10 percent of the size of our own Milky Way," says Ryan Hickox, an assistant professor in Dartmouth's Department of Physics and Astronomy. "If you look at it, it's a blob, but it surprisingly harbors a central black hole."

51 Pegasi b, about 50 light-years from Earth in the constellation of Pegasus, was discovered in 1995 and was the the first confirmed exoplanet to be found orbiting an ordinary star like our Sun. It is the archetypal Hot Jupiter -- a class of planets similar in size and mass to Jupiter but orbiting much closer to their parent stars.

Since that landmark discovery, more than 1,900 exoplanets in 1,200 planetary systems have been confirmed, but 51 Pegasi b now has another "first" - it has been directly detected in visible light.

Astronomers have found evidence of a giant void that could be the largest known structure in the universe. The “supervoid” solves a controversial cosmic puzzle: it explains the origin of a large and anomalously cold region of the sky. However, future observations are needed to confirm the discovery and determine whether the void is unique.

In 2004, astronomers examining a map of the radiation leftover from the Big Bang (the cosmic microwave background, or CMB) discovered the Cold Spot, a larger-than-expected unusually cold area of the sky. The physics surrounding the Big Bang theory predicts warmer and cooler spots of various sizes in the infant universe, but a spot this large and this cold was unexpected.

Now, a team of astronomers led by Dr. Istvan Szapudi of the Institute for Astronomy at the University of Hawaii at Manoa may have found an explanation for the existence of the Cold Spot, which Szapudi says may be "the largest individual structure ever identified by humanity."

On Oct. 12, 2017, the asteroid 2012 TC4 is slated to whizz by Earth dangerously close.

The exact distance of its closest approach is uncertain, as well as its size.

Based on observations in October 2012 when the space rock missed our planet, astronomers estimate that its size could vary from 12 to 40 meters. The meteor that exploded over the Russian city of Chelyabinsk in February 2013, injuring 1,500 people and damaging over 7,000 buildings, was about 20 meters wide.

Astronomers and planetary scientists have been waiting with bated breath for the first detailed close-up images of Ceres, the solar system’s largest asteroid. Now, with NASA’s Dawn spacecraft approaching closer each day, tantalizing new color imagery has revealed new details of the geological processes that formed Ceres.

New Horizons will soon reach Pluto, and is expected to find new moons and possibly a ring system. Could it find a moon of a moon? Or a moon with rings?

As we search for an answer, we will find out about why our Moon finds it hard keep a satellite at all, even just for a few years, and why an early satellite released by Apollo 16 unexpectedly crashed into the Moon. Also we'll chase up an intriguing puzzle about Saturn's moon Rhea.

Let's start with our own Earth / Moon system. Why is the Moon's orbit stable - and why can't our Moon have moonlets, or can it?

A team of astronomers studied the simultaneous collision of four galaxies in the galaxy cluster Abell 3827 and could trace out where the mass lies within the system and compare the distribution of the dark matter with the positions of the luminous galaxies.

Although dark matter cannot be seen, the team could deduce its location using a technique called gravitational lensing. The collision happened to take place directly in front of a much more distant, unrelated source. The mass of dark matter around the colliding galaxies severely distorted spacetime, deviating the path of light rays coming from the distant background galaxy -- and distorting its image into characteristic arc shapes.