A big rock for Valentine’s Day? Watch our VP of Astronomy Carolyn Sumners discuss the massive asteroid zooming past Earth on Feb. 15

If you anticipated seeing stars this Valentine’s Day, you weren’t far off.

Asteroid 2012 DA14 is projected to pass “dangerously close” to earth Feb. 15 — potentially taking out some important communication satellites.

Carolyn Sumners talks Valentine's Asteroid on MyFoxHouston

Discovered last year, the asteroid is half the length of a football field, weighs 130,000 metric tons and will pass Earth at a closer distance than the Moon at some 17,000 miles per hour. But astronomers, including HMNS’ own VP of Astronomy Carolyn Sumners, have put our stammering hearts to rest — sort of:

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“Asteroids this size – the one we’re talking about for next week – can destroy a city, not a planet,” Sumners told MyFoxHouston.

Luckily, NASA says there’s no chance of impact. This year, the cosmic love’s on you.

Don’t miss the Geminid Meteor Shower this Friday night! Here’s how, where and when to view

The annual Geminid Meteor Shower peaks this weekend, and we’ve got some tips for stargazers hoping to catch it.

The New Moon falls on Thursday, Dec. 13 this year, which should guarantee us nice, dark night for viewing. The Geminid Meteor shower peaks every December and is one of the best, most reliable showers, producing an average of 100 meteors per hour.

A Geminid meteor in 2009, as viewed from San Francisco
A Geminid meteor in 2009, as viewed from San Francisco, courtesy of Wikimedia Commons

Says HMNS Astronomer James Wooten: “The Geminids are unique among meteor showers because they are associated not with a comet but with an asteroid, 3200 Phaethon. This means that with Geminids, we see significant activity much earlier in the night than with other showers.”

That means instead of having to wait until the wee morning hours to see this beautiful shower, meteors will start radiating from the constellation Gemini as early as 9 or 10 p.m., although the shower will likely peak just before dawn.

As with all showers, the Geminid Meteor Shower will be best viewed away from city light pollution. The George Observatory will be open Friday night and into Saturday morning for observation. For directions to The George, located just an hour south of Houston, click here. Entry to Brazos Bend State Park is $7 per person; free for kids under 12. You don’t need any special equipment for viewing, just a chair, blankets and maybe some hot apple cider.

If you observe the meteor shower and are able to capture some great photos, share them with our Flickr group or by using the hashtag #hmnsgeminid on Twitter and Instagram. If Facebook’s your thing, post your photos on our wall, or tag us, and we’ll compile a credited album of everyone’s shots!

Science Doesn’t Sleep (9.4.08)

Released to Public: Astronaut Robert L. Curbeam, Jr., STS-116 Spacewalk (NASA)
“Houston…we’ve got a
SPAM problem.”
Creative Commons License photo credit:
pingnews.com

So here’s what went down after you logged off.

There’s a new Manhattan floating around the Arctic – and it’s made of ice. Canada’s polar ice shelves are “crumbling at an alarming pace.” In other good news: sea levels will rise much faster than we thought.

It’s possibly the lamest thing ever done in space: yesterday, astronauts spent some time updating their antivirus software.

It was the fake mustaches that tipped them off. Up to 10 percent of Near Earth Objects are comets impersonating asteroids - and new research aims to unmask them.

It’s really, really big: a black hole as big as 50 billion suns.

The ocean has its own lakes – called meddies – and scientists are using oil industry tech to study them.


Eight is Enough?

Creative Commons License photo credit: CommandZed

Two years ago this month, the International Astronomical Union adopted a new definition of ‘planet’ which excludes Pluto. Not only do I, as Planetarium Astronomer, continue to get questions about Pluto’s ‘demotion’, but scientists themselves continue to debate it. Right now (August 14-16, 2008), a conference called “The Great Planet Debate:Science as Process” is underway at the John’s Hopkins University Applied Physics Laboratory in Laurel, Maryland. The saga of Pluto and of the definition of ‘planet’ offers some insight into our solar system and into how science works.

northern tier sky
Creative Commons License photo credit: truello

The definition of ‘planet’ has changed before. Ancients looked at the sky and saw that certain ‘stars’ in the sky changed position, while most stars seemed to form the same patterns all of the time. The Ancient Greeks called the moving stars ‘planetes‘, or wanderers–this is the origin of the word. The Moon, too, appears near different stars each night. The Sun’s apparent motion is less obvious, since we don’t see the Sun and stars at the same time. Careful observers, however, can see that different stars rise and set with the Sun at different times of year. The full list of ‘planetes’, then, included the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. (Astrologers still use this archaic definition of planet).

Thanks to Copernicus and Galileo, people began to realize that the Sun, not the Earth, was the center of the solar system. The definition of ‘planet’ changed from ‘object which moves against the background stars’ to ‘object in orbit around the Sun’. The Sun and Moon, which had been planets, no longer were.

The position of Uranus, discovered in 1781, seemed to fit a pattern described by astronomers Johann Titius and Johann Bode. That same ‘Titius-Bode rule’ also predicted a planet between Mars and Jupiter, so when Giuseppe Piazza discovered Ceres at just the right distance in 1801, it was considered a planet. By 1807, four new ‘planets’ had been found between Mars and Jupiter (Ceres, Pallas, Juno, and Vesta). By the middle of that century, however, dozens of these new objects were being discovered; up to 100 had been found by 1868. It thus became clear that astronomers had in fact found a new category of solar system object. Astronomers adopted the term ‘asteroid‘, which William Herschel had recommended in 1802; ‘planet’ was redefined to exclude very small objects that occur in bunches. This is how science works; we must constantly revise even long standing definitions as we learn more about the universe around us.

In the late 19th century, astronomers noticed that Uranus and Neptune seemed to deviate ever so slightly from their predicted positions, suggesting that another planet was perturbing them. in 1906, Percival Lowell started a project to find the culprit, which he called ‘Planet X’. In 1930, Clyde W. Tombaugh located Pluto in sky photographs he took at Lowell Observatory in Arizona. It soon became apparent, however, that Pluto was not massive enough to influence the orbits of Uranus or Neptune. Throughout the mid 20th century, astronomers continued to revise Pluto’s estimated size downwards. From 1985 to 1990, Pluto’s equator was edge on to us, such that we saw its moon Charon pass directly in front of and behind Pluto’s disk. This allowed scientists to measure Pluto’s diameter more precisely, proving that it had not been the Planet X that Percival Lowell sought. Pluto’s diameter is just under 2400 km, a little less than the distance from the Rio Grande to the US/Canadian border. Pluto’s discovery, it turns out, was an accident.

In addition to small size, Pluto has an unusual orbit. Planetary orbits are ellipses rather than perfect circles. The eccentricity of an ellipse indicates how ‘out-of-round’ it is on a scale from 0 (perfect circle) to 1 (parabola–far end at infinity). Pluto’s orbit has an eccentricity of about 0.25, much greater than that of planets such as Earth (0.01) or Venus (0.007). The planets orbit nearly (but not exactly) in the same plane; Mercury‘s orbit, inclined by 7 degrees, is the most ‘out of line’. Pluto’s orbit, however, is inclined by 17 degrees.

Released to Public: Solar System Montage (NASA)

Behold: a pluto-less solar system.
Creative Commons License photo credit: pingnews.com

We divide the planets of our solar system into two categories: the inner planets (Mercury, Venus, Earth, and Mars) which are made mostly of rock, and the outer planets (Jupiter, Saturn, Uranus, and Neptune) which are gas giants with no solid surface. Pluto, however, fits in neither of these categories, as it is made of ice and rock (by some estimates, it’s 70% rock and 30% ice; by others, it’s about 50/50).

With its small size and abnormal orbit and composition, Pluto was always a misfit. Textbooks noted how Pluto fit in with neither the rocky inner planets nor the gas giants in the outer solar system. Still, Pluto remained a ‘planet’ because we knew of nothing else like it. There was simply no good term for what Pluto is.

That began to change in 1992, when astronomers began finding Kuiper Belt objects. The Kuiper Belt is a group of small bodies similar to the asteroid belt. Kuiper Belt objects (KBOs), however, orbit beyond Neptune’s orbit. Also, the Kuiper Belt occupies more space and contains more mass than does the asteroid belt. Finally, while asteroids are made mostly of rock, KBOs are largely composed of ice, including frozen ammonia and methane as well as water–just like Pluto. In addition to the Kuiper Belt proper, there is a scattered disc of objects thought to have been perturbed by Neptune and placed in highly eccentric orbits. Objects in the Kuiper Belt, scattered disc, and the much more distant Oort Cloud are together called Trans-Neptunian Objects (TNOs)

With the discovery of more and more KBOs, astronomers began to wonder if Pluto might fit better in this new category. Not only was the composition similar, but there is even a group of KBOs called plutinos, with orbits similar to Pluto’s. In the Kuiper Belt and the scattered disc, astronomers began to find objects approaching Pluto’s size, including Makemake, Quaoar, and Sedna.

Pluto can't get no respect
Pluto takes advantage of the wildly (?)
popular LOLcats to plead its case
with mankind.
Creative Commons License photo credit: the mad LOLscientist

To call Pluto a planet, but not these others, seemed arbitrary.

Finally, in 2005, a team of astronomers located Eris, which is slightly bigger than Pluto. Clearly, Eris and Pluto are the same kind of thing; either both are planets or both are not. If they both are planets, however, then should we include Quaoar et al., above? We have only just begun to explore and understand the Kuiper Belt and the scattered disc. Might we eventually find dozens of new ‘planets’ like Eris? Hundreds? Thousands?

This is what led the International Astronomical Union to reconsider the definition of ‘planet’ two Augusts ago. The IAU decided it was simpler to limit the number of planets to eight (Mercury through Neptune) and classify Pluto (and Eris, Quaoar, et al.) among the Trans-Neptunian objects. A new term, “dwarf planet,” includes the biggest asteroids and TNOs–those big enough to have assumed a spheroid shape. Still, other astronomers remain dissatisfied, hence the discussion going on in Maryland now.

There are two things we must keep in mind if we’re wondering when the Pluto question will be ‘resolved.’ First, decisions and conclusions of scientists are not holy edicts to be obeyed and never questioned. Quite the contrary, all such conclusions are provisional, pending new discoveries and better information. Any new decision reached this weekend is likely to be revised when the IAU meets again in 2009, and again in 2015 when the New Horizons mission arrives at Pluto. If it were any other way, science could not function.

Secondly, all categories which help us organize and understand things in our minds (including ‘planet’) are pure human inventions that only roughly correspond to nature. Although we need to categorize the things we see, nature does not; no matter how we classify objects, nature presents us with borderline cases that challenge us. Pluto is the same thing today as it was in 2005 or even before it was discovered in 1930. We need to distinguish our need for neat categories from our need to explore and describe nature.

Proud to be a space cadet? Learn more about astronomy:
Dust off your telescope – or visit the George Observatory – to see what’s in the night sky this month.
Ten billion trillion trillion carats – the universe has great taste in diamonds
If it blew a hole in your roof, you’re on the right track – how do you tell a rock might be a meteorite?