Published by NASA
Link to article with video: https://www.jpl.nasa.gov/video/details.php?id=1588
Link to page: International Observe the Moon Night, Oct 5, 2019
What can you see in the October sky? Join the global celebration of International Observe the Moon Night on Oct. 5th, then try to catch the ice giant planets Uranus and Neptune, which are well placed for viewing in the late night sky.
What’s Up for October? A night for the whole world to observe the Moon and hunting for ice giants!
International Observe the Moon Night is Oct. 5th. It’s an annual celebration of lunar observation and exploration. Events are scheduled in lots of places around the world, so there may be one near you. But all you really need to participate is to go out and look up.
The event is timed to coincide with the first quarter moon. This allows for some great observing along the lunar terminator – the line that divides the dayside from the nightside. With even a small pair of binoculars, you can see some great details as features like mountains and craters pop up into the light. Learn more and look for events in your area at moon.nasa.gov/observe.
October is a great time to try and capture an ICE GIANT. Now, these aren’t mythical creatures. They’re planets – the most distant of the major planets of our solar system, Uranus and Neptune.
The four giant planets of our solar system are not created equal. The gas giants, Jupiter and Saturn, are much bigger and way more massive, while the ice giants are so named because they contain a much higher amount of materials that typically form ices in the frigid depths of the outer solar system.
In October, both Uranus and Neptune are well placed in the late night sky. In fact, you can see all four giant planets in the same evening if you look for Jupiter and Saturn in the west after sunset, and then come back a couple of hours later to spot Uranus and Neptune. (Think of it as your own personal “Voyager mission.” NASA’s Voyager 2 is the only spacecraft to have visited the ice giants so far, although scientists are eager to go back for a more detailed study.)
Unlike Jupiter and Saturn, the ice giants are quite faint, so the best way to observe them is with a telescope, and from personal experience, it’s much easier to find them if you have a computer-controlled mount that can automatically point the telescope for you. If you don’t have access to one, find a local event with the Night Sky Network at nightsky.jpl.nasa.gov. Otherwise, sky watching apps can help you star-hop your way to these two incredibly distant planets.
Now be advised, because they’re so far away, each planet appears as just a point of light. But with a modest telescope, you’ll see Uranus as a tiny disk. You’d be forgiven for mistaking Neptune as a star – it’s the same size as Uranus, but much farther away, so it’s fainter.
The ice giants are elusive, but well worth the effort to say you’ve seen them with your own eyes.
Here are the phases of the Moon for October. You can catch up on all of NASA’s current and future missions at nasa.gov. I’m Preston Dyches from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.
A long standing question in cosmology is whether gravitational lensing changes the distance-redshift relation $D(z)$ or the mean flux density of sources. Interest in this has been rekindled by recent studies in non-linear relativistic perturbation theory that find biases in both the area of a surface of constant redshift and in the mean distance to this surface, with a fractional bias in both cases on the order of the mean squared convergence $langle kappa^2 rangle$. Any such area bias could alter CMB cosmology, and the corresponding bias in mean flux density could affect supernova cosmology. Here we show that, in an ensemble averaged sense, the perturbation to the area of a surface of constant redshift is in reality much smaller, being on the order of the cumulative bending angle squared, or roughly a part-in-a-million effect. This validates the arguments of Weinberg (1976) that the mean magnification $mu$ of sources…
View original post 151 more words