Observing The Sky
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This article is one of a series on how readers can learn the skills to participate in activities academics enjoy doing on the job.
My favorite part of my work as an astronomer is those rare moments when I see beautiful distant galaxies, whose light left them millions if not billions of years ago. It is a combination of sheer awe and scientific curiosity that excites me about the ‘galaxy hunt’.
In astronomy today, much of our work involves processing huge amounts of data by writing and running programs to work with images of the sky. One downside is that we don’t always have that “hands-on” experience of looking at every square inch of the universe as we study it. I’ll show you, however, how I get my dose of wonder watching galaxies that only a select few will ever see, so far.
In just our observable universe we estimate that there are over 2,000 billion galaxies!
Read more: Curious Kids: how are galaxies formed?
Galaxies at your fingertips
Only a few decades ago, astronomers had to tediously examine photographic plates after a long, cold, and lonely night of observation. In the 21st century, we have access to information anytime, anywhere via the Internet.
Telescopes and automatic surveys now provide us with so much data that we need machines to help us analyze it. In some cases, human eyes will only look at what computers have found interesting! Massive amounts of data are hosted online, just waiting to be admired, for free.
Read more: Powerful new telescopes allow direct imaging of nascent galaxies 12 billion light years away
Go online for an atlas of the universe
Aladin Lite is one of the best online tools available for viewing our universe through the eyes of many different telescopes. Here we can scan the entire sky for hidden galaxies and even decipher information about their populations and stellar evolution.
Let’s start our Universal Tour by searching for one of the most breathtaking galaxies, the Cartwheel Galaxy. In Aladdin’s interface, you can search for both the popular name of an object (such as “wheel galaxy”) or known coordinates. The location will be centered in the interface.
The first image of the Cartwheel galaxy that we see comes from optical imagery from the Digitized Sky Survey. The colors we see represent different filters of this telescope. However, these are pretty representative of what the galaxy would look like with our own eyes.
A general rule of thumb as an astronomer is that differences in “color” within galaxies are due to physically different environments. It’s important to note that things that look blue (shorter wavelengths) are generally warmer than things that look red (longer wavelengths).
In this galaxy, the outer ring appears to be bluer than the central red part. It could allude to star formation and stellar activity happening in the outer ring, but less in the center.
To confirm our suspicion of star formation, we may choose to examine data from different surveys, in different wavelengths. When young stars are formed, large amounts of UV radiation are emitted. By changing the reading to GALEXGR6 / AIS, we are only looking at UV wavelengths, and what a difference that makes!
The entire central part of the galaxy seems to “disappear” from our image. This suggests that the section is probably home to older stars, with fewer activities. stellar nurseries.
Aladdin is home to 20 different investigations. They provide imagery of the sky from optical, UV, infrared, X and gamma rays.
When I roam the universe looking for interesting galaxies here, I usually start in optics and find ones that I think are interesting. I then use the different surveys to see how the images change when looking at specific wavelengths.
Universal Where is Wally
Now that you’ve taken a crash course in Galaxy Hunting, let’s start the game! You can spend hours exploring the amazing pictures and finding interesting galaxies. I recommend looking at images from DECalS / DR3 for the highest resolution and detail when zoomed in.
The best method is to simply drag the atlas of the sky. If you find something interesting, you can find out all the information we have about it by selecting the target icon and clicking on the object.
To help you on your galactic expedition, here are my favorite finds of the different types of items you might see.
Spiral galaxies usually have a rotating central disc with large, spiraling “arms” curving from the denser central regions. They are incredibly beautiful. Our own Milky Way is a spiral galaxy.
Read more: Is our Milky Way galaxy a zombie, already dead and we don’t know?
Elliptical galaxies are largely featureless and less “flat” than spirals, with stars sometimes occupying almost a 3D ellipse. These types of galaxies tend to have older stars and less active star-forming regions than spiral galaxies.
Lenticular galaxies appear like cosmic pancakes, quite flat and without relief in the night sky. These galaxies can be thought of as the “in-between” of spiral and elliptical galaxies. Most of the star formation has stopped, but lenticular galaxies can still contain significant amounts of dust.
There are also other amazing types of galaxies, including mergers and lenses, who are waiting for you to find them. I’d love to see what amazing things you find on Twitter at @sarawebbscience.
Read more: 5 Ways Families Can Benefit From Astronomy During The Pandemic
You can read more articles in this series here.
