Category Archives: hubble space telescope

hubble space telescope, pleiades

Calling All Pleiadeans

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Courtesy Space Telescope Science Institute.
Courtesy Space Telescope Science Institute.

The Pleiades—that little cluster of stars that makes wintertime stargazing so nice (among so many other other night-time delights) came in for some extra interest by Hubble Space Telescope recently. Astronomers wanted to determine the distance to this little grouping. It’s not always been easy to tell how far away they are, and in fact their distance has been the subject of controversy among astronomers.

Measurements made by the Hipparcos satellite suggested that they were closer to Earth than observers used to think. However, other astronomers measured the distance and found it to be farther out. HST’s studies found the same result: the Pleiades lie about 440 light-years away from us. The image above shows the Pleiades with Hubble’s field of view superimposed over parts of the cluster.

Why all the fuss? Because if those stars lay farther away (as Hipparcos suggested) their brightness wouldn’t match with what we know about star characteristics (particularly sun-like stars).

It may seem like a tweak in distance measurements, but it’s an important one if we are to understand how stars form and how they live. Astronomy is often like that— giving us tantalizing hints about the nature of objects and leaving it up to us to measure and chart the details.

So, if you’re a Pleiadean (one interested in this glittery little set of stars, not necessarily someone who thinks you’re from the Pleiades), take heart: from 440 light-years away, they’re helping us understand more about stars like our Sun.

dwarf planets, hubble space telescope, planets

Sedna: The Latest of the Outermost Objects in the Solar System

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Sedna
Sedna

You gotta love the Hubble Space Telescope. There it is up there, looking out across the deeps of space and time, spotting shreds of galaxies as they formed some 300,000 to 500,000 years after the Big Bang, and then it turns around and gives us a view of a little shard of a world called Sedna. This place, smaller than the Moon, smaller than Pluto, lies about 90 times the distance between the Earth and Sun, out in a region of the solar system called the Kuiper Belt. It’s a leftover bit of ice (mostly) from the formation of the solar system some 5.5 billion years ago. It’s so dim and small that HST’s image is one pixel across. But, it’s an informative pixel!

For instance, it tells us that (so far) HST hasn’t spotted a companion to this planetoid, although the astronomer who discovered it on March 15, 2004, calculated its spin rate (it’s “day”) and determined that it should have a moon of some kind. The fact that it doesn’t illustrates one of those wonderful “non-results” that tells us valuable information. Science is replete with stuff like this — what looks like a non-result actually helps us put limits on an object’s actions or size or mass or other characteristic. It reminds me of the observation run I did in Hawaii where we studied Comet Hale-Bopp in late 1996. We thought we might be able to spot a plasma tail forming earlier than might be expected. However, when we examined the data, we found no evidence of the plasma tail, which told us that even with a comet of that size, it had to be close enough to the Sun (essentially within about 2 to 2.5 AU of the Sun) before its plasma tail would form. It helped us nail down parts of a descriptive theory we were formulating about how and when and why these glowing tails form when they do as a comet approaches the Sun during its orbit.

Astronomers will keep studying Sedna, and in fact, they have looked at it with other telescopes since its discovery. Expect to see a few more announcements about this frigid world at the frontiers of the solar system!