SUNSET: 
What the Discovery of Massive Early Galaxies Could Mean for Cosmology
JWST's detection of early galaxies that are far more massive than astronomers had expected could mean we need to rewrite our understanding of the cosmos.
Webb Telescope Sees Deep and Wide into the Universe
A new deep field from the James Webb Space Telescope shows how galaxies evolved in the early universe.
Webb Telescope Shatters Distance Records, Challenges Astronomers
Distant galaxies in Webb images suggest we need to rethink star and galaxy evolution in the early universe.
How Many Galaxies Are There in the Universe?
Astronomers determine the number of galaxies in the universe by counting up the number visible in a tiny portion of the sky, and then accounting for all the regions of the observable universe. A 2013 study estimates that there are 225 billion galaxies in the observable universe.
How many digits are satisfactory in the measurement of pi?
In the 3rd century BC, Archimedes proved that the ratio of a circle’s circumference to its diameter is less than 3 1/7 but larger than 3 10/71. That’s about 3.141. Later mathematicians have computed what we now call p (pi) to greater and greater accuracy — but how many digits…
What percentage of our galaxy’s stars move in retrograde orbits?
Do astronomers have any idea what percentage of our galaxy’s stars move in retrograde orbits? The short answer is yes, a very small percentage. But the long answer is more interesting. First, let’s agree what we mean by “retrograde.” If you were to look down on the solar system from…
Why are the Large and Small Magellanic Clouds not listed among the Caldwell objects?
Why are the Large and Small Magellanic Clouds not listed among the Caldwell objects? They are also not given in Stephen James O’Meara’s book The Messier Objects in the list of 20 spectacular non-Messier objects nor among O’Meara’s 20 spectacular non-Caldwell objects in The Caldwell Objects. Are they too bright?…
Where was the Big Bang located?
The commonest misconception about the Big Bang is that it happened at some particular spot in preexisting empty space.
Should you use light-years or parsecs for astronomical distance?
You give astronomical distances beyond the solar system in light-years, but professional astronomy papers use parsecs. Which is preferable? Light-years, no question! Here’s how I see it. The parsec (which equals 3.26 light-years) is defined as the distance at which a star will show an annual parallax of one arcsecond.…
When we say a galaxy is 300 million light-years away is that its distance now or 300 million years ago?
When we say a galaxy is 300 million light-years away, is that its distance now or 300 million years ago? Oftentimes, neither! In most cases astronomers try to get a handle on a galaxy’s distance by measuring its redshift: the degree to which the universe’s expansion has stretched its light…
What's the most distant object I can see with my telescope?
Is there a more distant object than NGC 4889 (Caldwell 35) that I can see with my 5-inch reflector? Yes, by a factor of 7! Think quasars. NGC 4889 is a member of the Coma Galaxy Cluster, which lies about 300 million light-years away. But the quasar 3C 273 is…
What's the density of the black hole in galaxy M87?
On page 20 of the March 2004 issue, you say the 3-billion-solar-mass black hole in the center of the galaxy M87 has an average density about that of air. I would love to understand how this makes any sense. The diameter of a black hole scales directly with its mass.…
