Category Archives: european southern observatory

One Star, Two Planets, Big News

What Are They Like?

This artist’s concept illustrates the two Saturn-sized planets discovered by NASA’s Kepler mission. The star system is oriented edge-on, as seen by Kepler, such that both planets cross in front, or transit, their star, named Kepler-9. This is the first star system found to have multiple transiting planets. Credit: NASA/Ames/JPL-Caltech

It has been almost 20 years since the first extrasolar planets (worlds around other stars) were discovered.  Astronomers suspected they existed, but since tiny worlds can get lost in the glare of their stars’ light, we had to wait until we had the right kinds of instruments to observe distant worlds circling other stars. Today, the number of confirmed exoplanets lies at just under 500, and that number changes almost daily.

The latest news in planet-hunting circles is the discovery of two planets orbiting a star called Kepler-9.  The planets showed up in data taken by the Kepler mission, which is tasked to search for extrasolar planets in an area of the sky in the direction of the constellation Cygnus the Swan (which is high in the northern hemisphere sky these evenings).

Now, there have been lots of extrasolar planets discovered, but this is the first time two have been confirmed orbiting the same star. The planets, named Kepler-9b and Kepler-9c, have masses that are almost that of Saturn in our own solar system. Kepler-9b is the larger of the two and it orbits the star once every 19 days. The smaller Kepler-9c lies farther away and takes 38 days to make a trip around the star.

The Kepler spacecraft observed this system to tack down the precise length of each planet’s orbit around the parent star. This isn’t the only such system that the spacecraft has data for, but it’s the first to be confirmed — a big milestone for the team and the spacecraft.

The planets were discovered as the Kepler spacecraft’s camera measured tiny decreases in the star’s brightness–decreases that occur when a planet moves between us and the star. And yes, even something so small as a planet can have an effect on the star’s brightness, and Kepler is sensitive enough to detect those little dips in the star’s light.  In addition, the distance between each planet and the star can be calculated by measuring the time between successive dips as the planet orbits the star. Small changes in the regularity of these dips can help astronomers determine the masses of planets and detect other non-transiting planets in the system. In fact, the data seem to indicate that there may be at least one other planet in the system–a world about 1.5 times the Earth’s radius that follows a scorchingly short 1.6-day orbit around the star. Kepler scientists are still taking data to make sure that this is another planet and not an anomaly in the data.

The artist’s concept of the two confirmed planets show that these are gas giant-like worlds, so they’re not likely to be places where life is going to exist — at least life as we know it. And, if there IS another planet that’s closer to Earth-size? Well, it’s not likely to be a very hospitable place either. It’s likely a scorchingly hot place with little opportunity for life to take hold.

Kepler’s discovery is the second in a pair of exoplanet finds reported this week. The European Southern Observatory announced earlier that it has found a star that may have at least five planets orbiting around it. Astronomers used the HARPS spectrograph attached to the ESO’s 3.6-meter telescope in Chile to search for the existence of planets in the system. Unlike the Kepler mission, which checks for dips in light intensity of stars with planets in orbit around them, the HARPS insrtrument looks for stellar motions that indicate the existence of planets. The amount of motion tells them the mass of the planets that may exist, and helps them deduce the orbits of those distant worlds. The measurements correspond to planets with masses between 13 and 25 Earth masses. They appear to orbit  the star with periods ranging from about 6 to 600 days. These planets lie between 0.06 and 1.4 times the Earth–Sun distance from their central star. This is actually pretty well-populated system with five massive planets located within 1.4 AU.  By comparison, the Sun has only four planets — and small ones at that — in roughly the same space.

The science of planetary detection is a major growth area in astronomy. With Kepler’s ongoing mission and the ground-based work being done at places such as ESO, I think it’s only a matter of time before the community of worlds that we can detect will be well over a thousand. Now… if we could only find one with life on it!

Adventures Beyond Imagination?

How About “Adventures Beyond Our Galaxy”

Think about the term “Beyond Imagination!”  Marketing people like to use it to sell media “experiences”.  I always wonder “If it’s beyond imagination, than how can we conceive of it, much less market it?”   Yeah, the term is a bit of hyperbole used to amp up excitement about something that the marketing folk think needs it.  Seems to me that if you need to amp up excitement, you’d better rethink your product.  But hey, that’s just me.

Astronomy is one of those subjects that I don’t think really needs any amping up. It gives you a free show ever night, and if you love the subject, gorgeous pictures and information about distant stars and galaxies is usually only a mouseclick away.

Astronomy is a science that brings its own adventure to you just by showing you how grand the cosmos is.  With that in mind, I’ve got something for you that’s not only well within our collective imagination — it’s fascinating, beautiful, and stunning.  You don’t have to tak my word for it — just look at the picture fr yourself, provided by the European Southern Observatory’s VISTA survey:

The Tarantula Nebula, with the 30 Doradus star-forming region (top) in all its celestial glory, as seen by the European Southern Observatory's VISTA survey telescope. Courtesy ESO. You MUST click to embiggenate.

What is it?  It’s a star-forming nebula that lies about 170,000 light-years away from us in a companion galaxy called the Large Magellanic Cloud.  This region is called the Tarantula Nebula and it has attracted astronomers to study it like moths are attracted to a light bulb.

This nebula, also called 30 Doradus, hosts the spectacular R 136 starbirth crêche at its heart.  Nothing here is beyond imagination, especially now that astronomers have a decent idea of the process of star formation.

It used to be (back in the early days of modern astronomy, say back in the late 1800s and the first part of the 1900s) that the births of stars was shrouded in mis-information and not a whole lot of understanding. This is because the details are hidden, veiled from us in a cloud of gas and dust that surrounds the nursery where stellar babies are coming to life. So, until astronomers of the last century could build telescopes with the right instruments (such as IRAS and HST and Spitzer) to peer through the clouds of and dust to send to space, or equip ground-based telescopes with the proper near-infrared instruments to do the same thing from Earth, plus ways to “get past” our atmosphere using adaptive optics, the details of star birth remained a secret. But, NOT beyond imagination. Astronomers had a pretty good theoretical idea of how it happened — they just needed good observational data to help cement the process of star birth together. And, studying places like R136 here in the Tarantula Nebula is one of the ways they get a chance to study more regions of star birth, to trace the progression from cloud of gas and dust to brilliantly shining star.  The more examples they study, the more astronomers understand how it works.  And, that makes the study of places like the Tarantula an adventure beyond our galaxy, but not beyond our understanding. I’d LOVE to turn it into a made-for-TV (or museum or fulldome planetarium) movie.  It would be cosmic adventure on a massive scale.

Any takers?