Category Archives: Observables

things we can see from Earth using our eyeballs or telescopes

Information About Eclipses

Here are some of my favorite sites for learning about eclipses (including the upcoming Great American Eclipse!):


“Moon Slide (slim)” from Astronomy Picture of the Day. This “Moon-trail” by Stefan Siep was created by just opening the shutter and keeping it open for about 3 hours. Note the brightness difference between full and eclipsed :)


2016 Planetary Alignment!

As described in class, here are my two favorite articles about this alignment:

Get Up Early, See Five Planets at Once! from Sky and Telescope

How to View Five Planets Aligning in a Celestial Spectacle from The New York Times

I happen to adore the NYT diagram because it shows the Solar System view as well as the view from Earth:

Screen Shot 2016-01-21 at 11.49.15 PM

View of planetary positioning from “above” the Solar System as well as the view from Earth (from the New York Times)

Planet Nine!

Caltech Researchers Find Evidence of a Real Ninth Planet

This is legit folks!  For those who are at a university (like Vanderbilt), this press release has a link to the actual research article in the Astronomical Journal.  It’s a bit heavy at times but well done.

There’s also a pretty good article on Wired: This Isn’t the First Time Astronomers Have “Found” a Planet Nine


(from the press release) The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the solar system. Batygin and Brown show that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration.

The 2017 Nashville Eclipse!

In class yesterday we talked about eclipses and so here’s the post about it!

The totally awesome (and very dedicated) Mr. Eclipse (i.e., The Ultimate Resource for Eclipse Photography) is a favorite of NASA so they use his diagrams on their eclipse website.

The foremost resource for the 2017 eclipse is  The Interactive Google Map they have linked is AMAZING.  The image below is from that map.  The Wikipedia article is pretty good as well.

Path of the 2017 Total Solar Eclipse.  Can't see totality unless within that line.

Path of the 2017 Total Solar Eclipse. Can’t see totality unless within that line.

On the map, you can zoom in and click on a location which will bring up information about time of partial eclipse start/end, totality start/end, duration of totality, and anything else you might need.  The map also has information for areas in the partial eclipse regions.

You should make plans!!

Ooo, you can also see a great map here of total solar eclipses in the US in the next 50 years!!  Make more plans!

The whole asteroid thing!

There have been some pretty amazing things going on with asteroids the past couple of days, namely the passing of Asteroid 2012 DA14 and the Russian Meteor Event.   But they were completely unrelated!  Here is an excellent infographic for you (click to make bigger):

Infographic from The Telegraph (UK)

Infographic from The Telegraph (UK)
– click to make bigger

We weren’t going to be seeing that little 50-foot asteroid coming at us from Sun-ward…  The Sun is the most powerful gravitational slingshot in the Solar System but if we know the trajectories of ALL little rocks in the Solar System, then we could know a bit more.  But it will take a LOT of observing time to see them…  These little ones (like the Russian one) are VERY difficult to see, I just don’t see us catching them all but we can sure try :)  I think we just need a big force field ;)

Here are some of my favorite posts about the Russian event:

Astronomically, it IS an early spring!!

So I read this article and I had to share it with you – I think it’s very good :)

Article:  Spring Arrives With Equinox Tuesday, Earliest in Over a Century
by Joe Rao, Skywatching Columnist

As an introduction, here in Nashville, we’ve been experiencing a really mild spring – personally, I’m pretty happy about it because I go observing with the lab students a lot and it’s been so nice to not have to bundle up ;)  Thus we’ve been having an early spring meteorologically.

But let’s think about what the start of spring means ASTRONOMICALLY.  The start of spring is technically the date of the vernal equinox which technically is when the Sun’s position in the sky goes from being in the southern celestial hemisphere to being in the northern celestial hemisphere.  You can see this with Stellarium!!  Plus you can see how the actual location of the equinox in the sky (comparing it to the constellations) changes over time – this is called the precession of the equinoxes and it is why we are entering the Age of Aquarius!

Heliocentric vernal equinox

The vernal equinox location (see arrow) according to the heliocentric perspective.

Geocentric vernal equinox

The location of the vernal equinox according to a geocentric view

Here’s a lovely graph from Wolfram Alpha that shows the date of the vernal (spring) equinox for certain time periods (see axes ;) ):

Date of the vernal equinox VS time - from Wolfram Alpha

Note that we’re bottoming out for our cycle in the left graph (stupid axes if you ask me so it is kinda hard to see).  The short-period cyclic nature on the left shows the “resetting” every leap year and then the big jumps on the right plot show the effect of not having a leap year during century years (i.e., 1800, 1900, 2100, 2200) unless those years are divisible by 400 (i.e., 2000).  To learn more about this (and to see a better graph), go to Wikipedia :)  Dudes, on Wikipedia, I learned about the Iranian calendar which has 8 leap days in every 33 year time period – it’s more accurate :)

Anyway, the aforementioned article is a good article – Dr. G approved! ;)

Go outside on March 12 and 13!!

Mercury, Venus, and the Moon aligned. Taken from Paranal Observatory in Chile, March 2008 by Yuri Beletsky.

Right when we come back from Spring Break, we will be able to see a planetary conjunction!  You will be able to see Jupiter and Venus be within three degrees of each other and that’s an especially close separation and will be especially brilliant due to the biology of your eyeball – they will be so close that the “hi-def” part of your eye (the fovea) will be activated.  Here is a NASA article about it: Cold and Spellbinding: An Alignment of Planets in the Sunset Sky

Note that this conjunction is just the kind of thing that early astronomers were trying to predict using the Geocentric (Ptolemaic) model of the Solar System (with all of the epicycles and such).  To be honest, the geocentric model worked pretty well at the beginning, but errors combined over the centuries.  This conjunction is also the kind of thing that astronomers used the Heliocentric model of Copernicus to predict but was just as inaccurate due to Copernicus’ need for perfect circles.  Kepler’s models helped take care of the prediction problems thus the heliocentric model became the accepted model of the Solar System :)

To see how the conjunction works, I’ve put a line on this picture from the NASA/JPL Solar System Simulator.  Note that the line from Earth passes by both Venus and Jupiter :)

Solar System on March 12, 2012

Solar System diagram for March 12, 2012 to illustrate the conjunction of Jupiter and Venus. Note that Venus and Jupiter are along the same line-of-sight from Earth.

Buying a star

Last week, I brought the portable planetarium that I run (the Fisk-Vanderbilt NASA Astronomy Roadshow) to a school north of Nashville.  From both the parents and the students, I got questions about buying a star for someone.  I get these questions a lot – from people when I do outreach, from friends for whom I’m “their” astrophysicist, from students…  It is a really nice idea and very sweet, but IT IS NOT WORTH IT.  Should you do buy a star for someone, you are giving your money away to some opportunists.  The star name company will give you a nice certificate, put your name in a database, and take $50 (or more).  However, there are several companies out there, each with their own databases, and they don’t talk to each other.  “Your” star could also be several other people’s star.  Also, the naming is in no way official – no astronomer will ever, EVER call your star by the name you “buy” – astronomers have our own, internationally agreed upon, usually boring numeric names/designations.

More importantly, the sky is free :)  We should keep it that way.

If you would like more information

Sirius and Long Exposure Photography!

Long exposure of Sirius with purposeful tripod vibration (found here)

This is very cool – both photographers and astronomers will like this :)

Above, you see an image (a picture) of the brightest star in the sky (besides the Sun), Sirius.  Sirius is part of the constellation Canis Major (The Greater Dog) – it is the eye of the dog.  It’s the namesake of SiriusXM Radio (see the (apparently former) logo).  It’s also the namesake of Sirius Black of Harry Potter fame!  What does Sirius Black turn into??  A dog!  A big black one!

Anyway, Sirius is seriously twinkle-y – stars twinkle due to the atmosphere (the atmosphere bubbles and boils and causes light to bend) – if you were in a spacecraft above the atmosphere, you wouldn’t see twinkle-y stars.  The photographer used the fact that the twinkling can change the color of the light that hits your eye (or the camera) because different colors are easier to bend than others (red is easiest, blue is hardest).

The image is a 5 second exposure with a telephoto lens and the tripod was specifically vibrated and taken by astronomer David Lynch.

I was made aware of this picture by Dr. Phil Plait, “The Bad Astronomer” – formerly an astronomy professor, now an author and blogger for Discover Magazine (a fave magazine of mine).

Radiation and Astronauts

from National Geographic - Biggest solar flare in 4 years

So the Sun flares and bubbles and boils – we’ll learn lots more about that later in the semester.  But when the Sun is doing its thing, what is happening to the astronauts?  And how can humans survive a trip to Mars?

A Facebook friend who works at Goddard Space Flight Center shared a photo and a post by a friend of hers who works with astronauts.  The source of the information in the post is actually from an article on NASA’s homepage and you can find it here.

On that page you’ll find graphs and links and a great description of why it’s actually kind of nice for astronauts to be in the “Solar Maximum” :)  How cool is that!  There are other links on that page to the “Phantom Torso” they study and you can find more for yourself.  In class, we’ll talk about some of the issues of human spaceflight during the last few days of class.

Reflecting, while I am an astrophysicist, I don’t want to be an astronaut right now (and actually never really have)…  Kinda odd many might assume…  But the thing is, I really REALLY want to go see stars and how they work and what weirdo ones look like up close!  But I can’t do that yet – we don’t have the technology :(  Until we do, I’ll keep my feet on the ground and watch the awesome data that comes back to us :)