Thing you need to see: All of Hubble’s Observations in One Picture! - Beyond The World
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Thing you need to see: All of Hubble’s Observations in One Picture!

Hubble has done about 1.4 million observations of our Universe in the last 32 years. Casey Handmer, a physicist, wanted to know how much of the sky Hubble had imaged, so he found out how to map out all of Hubble’s observations into one enormous picture of the sky.

It’s a lovely, almost poetic glimpse of Hubble’s overall picture of the universe. So, how big is Hubble’s view of the sky? You might be surprised by the response.

Handmer thought about it and calculated that, with Hubble’s range of vision of 202 arc seconds, covering the sky would take around 3.2 million observations. Would Hubble have seen nearly half of the universe if it had performed 1.4 million observations since its inception in 1990?

“I ran a basic calculation and I think it’s around 0.8% of the entire sky has been exposed to the Hubble imaging system,” Handmer said via email, adding that the answer is not as simple as counting the dots in the image because the poles are actually quite stretched on this map.

All of the Hubble Space Telescope’s observations from the past 32 years, shown in one graphic. Credit and copyright: Casey Handmer. Used by permission.

But why such a meager sum? Handmer explained that there are several causes behind this. For example, the spectrometer instruments aren’t always creating a picture. Another reason is that Hubble’s range of vision is quite limited when compared to telescopes designed to conduct all-sky surveys. But another big reason is that Hubble tends to view certain areas of the sky or certain astronomical objects repeatedly. Why? Because it is exactly what scientists are looking for. Some observations are more time consuming than others, and some sections of the sky are more interesting than others.

The curved line across the centre of Handmer’s image symbolizes the ecliptic, indicating Hubble’s extensive (and repeated) observations of planets, moons, and asteroids in our own Solar System.

The huge and small Magellanic clouds, which orbit (and are progressively consumed by) our own galaxy, are the two massive lumps near the bottom left. Other nearby galaxies make up many of the other clusters. The Milky Way’s disk is also seen as a dark U-shaped curve running through the center.

As a result, this graphic exemplifies what Hubble excels at.

“Hubble is best used for deep space observations,” Handmer said. “It wasn’t designed to be an all-sky survey telescope, and so and zooming around would undermine the telescope’s ability to stare at really tiny really dim objects for a long time to gain valuable data.”

The Vera Rubin Observatory, on the other hand, will photograph the entire sky every week, according to Handmer (the observatory is set to open late next year).

Handmer used the Astropy Library’s astroquery API to obtain data on every Hubble observation to make this image. You can find the code Handmer used here.

“Each of the observations recovered using the API describes the target, but in the aggregate, we get a picture of what Hubble is looking at,” Handmer said. “Hubble is an amazing instrument but it has been in space for almost 32 years and will not last forever. We are fortunate to finally have JWST launched and operating but imagine what we could see if we launched a new telescope like this every year!”

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