Category Archives: Hubble Space Telecope

Hubble Space Telecope, neptune

It Was There All Along

6 Comments

Hubble Space Telescope Images Reveal Neptune’s Moon

This composite Hubble Space Telescope picture shows the location of a newly discovered moon, designated S/2004 N 1, orbiting the giant planet Neptune, 4.8 billion kilometers from Earth. The moon is so small (no more than 12 miles across) and dim, it was missed by NASA’s Voyager 2 spacecraft cameras when the probe flew by Neptune in 1989. Several other moons that were discovered by Voyager appear in this 2009 image, along with a circumplanetary structure known as ring arcs. The black-and-white image was taken in 2009 with Hubble’s Wide Field Camera 3 in visible light. Hubble took the color inset of Neptune on August 19, 2009. Credit: NASA, ESA, and M. Showalter (SETI Institute).

Neptune is the most distant planet in our solar system, which makes its systems of moons and rings a challenge to observe from Earth. These things are small and dim, even in Hubble Space Telescope images and data.

On July 1, Dr. Mark Showalter, a scientist at the SETI Institute in California, spotted something in Hubble images that hadn’t been seen before circling around the giant planet. Or least, it hadn’t been seen by human eyes. It was a small moon orbiting the planet about once every 23 hours. He was actually studying faint arcs (segments) of rings. “The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system,” he said. “It’s the same reason a sports photographer tracks a running athlete—the athlete stays in focus, but the background blurs.”

It turns out that this little moon, now dubbed S/2004 N1, was in images taken by Hubble between 2004 and 2009, but it’s extremely small and dim. It’s likely no one was looking directly for that moon, so it remained hidden in the data archives, waiting for Dr. Showalter to find it.

This finding is a great example of archival discoveries—that is, findings made as astronomers go back through earlier observations. They do this for a variety of reasons. Sometimes it’s to check and see if the object ever appeared to observers before. Or, as in the case of a supernova explosion, to see what the object that exploded looked like in earlier observations. Or, sometimes, they do it to chart change over time (for example, changes on the surface of Mars).

Prior observations of astronomical objects through the world’s panoply of telescopes (both ground-based, orbiting, and in situ (at planets) give us a good feel for how the planets, moons, rings, and distant objects like stars, nebulae, and galaxies change over time. The universe is a constantly evolving place, and it will always provide us with new objects and events to discover and study.

Hubble Space Telecope

Exploring the Universe

Leave a comment

It Begins Here at Home, Part II

One of the things I absolutely love about astronomy is that it’s just outside the door. You go out, you look up and you see things. During the day you know the Sun’s there, and part of the month you can also see the Moon.  At night, the stars are there for your exploration, along with the planets, and an amazing array of deep-sky objects such as nebulae.  What if you had such concentrated and perfect eyesight that you could look across more than thirteen billion light-years of space to some of the earliest galaxies and galaxy “seedlings” ever formed?  Well, people right here on Earth can do that. They’re using a magnificent time machine called the Hubble Space Telescope to do it.

The Hubble eXtreme Deep Field (XDF). My gosh, it’s full of galaxies! Courtesy STScI/NASA. (Click to embiggenate)

Over a period of ten years, astronomers have aimed the telescope at a patch of sky in the constellation Fornax and taken images of distant galaxies in that direction. They’ve essentially used HST as a big light bucket for a decade to collect faint light streaming from thousands of galaxies.

The resulting image is called the Hubble eXtreme Deep Field (XDF), and it has gorgeous spiral galaxies similar in shape to our Milky Way and the neighboring Andromeda Galaxy.  There are also large, old fuzzy red galaxies where the formation of new stars has shut down.

If you look closely at the large version of this image, you’ll find tiny, faint, and extremely distant galaxies sprinkled across the image. Think of these as the “seedlings” from which today’s  striking galaxies grew.

This whole image is basically a history of galaxy formation — from the first shreds of galaxies to the enormous and grand galaxies we see today in near-Milky Way space.
Hubble used two instruments to get this image. It took the Advanced Camera for Surveys and the Wide Field Camera 3 to get this level of detail from 2,000 images taken over a total exposure time of 2 million seconds spread out over ten years.  Why take so long?  The longer you look, the deeper you look, and the deeper you look, the further back in time you see. Thus, Hubble is really a time machine, showing us the distant universe — all the while orbiting Earth and sending back data and images to astronomers right here on the planet.  It’s really pretty amazing when you think about it.

To learn more about this image, surf on over to the Hubble Space Telescope Web site, and feast your eyes on bigger versions of this image. It’s worth exploring!