Southern California got all shook up after a set of recent quakes. But Earth isn't the only place that experiences quakes: Both the Moon and Mars have them as well. NASA sent the first seismometer to the Moon 50 years ago, during the Apollo 11 mission; the agency's InSight lander brought the first seismometer to Mars in late 2018, and it's called the Seismic Experiment for Interior Structure (SEIS).
The hunt for other planets in our galaxy has heated up in the past few decades, with 3869 planets being detected in 2,886 systems and another 2,898 candidates awaiting confirmation. Though the discovery of these planets has taught scientists much about the kinds of planets that exist in our galaxy, there is still much we do not know about the process of planetary formation.
The Solar System is a beautiful thing to behold. Between its four terrestrial planets, four gas giants, multiple minor planets composed of ice and rock, and countless moons and smaller objects, there is simply no shortage of things to study and be captivated by. Add to that our Sun, an Asteroid Belt, the Kuiper Belt, and many comets, and you’ve got enough to keep your busy for the rest of your life.
The Solar Planets are a nice mixed bag of what is possible when it comes to planetary formation. Within the inner Solar System, you have the terrestrial planets – bodies that are composed primarily of silicate minerals and metals. And in the outer Solar System, you have the gas giants and bodies that are composed primarily of ice that lie just beyond in the Trans-Neptunian region.
The Kepler space telescope is surely the gift that keeps on giving. After being deployed in 2009, it went on to detect a total of 2,335 confirmed exoplanets and 582 multi-planet systems. Even after two of its reaction wheels failed, it carried on with its K2 mission, which has discovered an additional 520 candidates, 148 of which have been confirmed. And with yet another extension, which will last beyond 2018, it shows no signs of stopping!
Pluto’s status as a “dwarf planet” is once again stirring debate. This comes as some planetary scientists are trying to have Pluto reclassified as a planet – a wish that’s not likely to come true.Pluto has been known as a dwarf planet for more than a decade. Back in August 2006 astronomers voted to shake up the Solar System, and the number of planets dropped from nine to eight. Pluto was the one cast aside.
The theory of how planets form has been something of an enduring mystery for scientists. While astronomers have a pretty good understanding of where planetary systems comes from – i.e. protoplanetary disks of dust and gas around new stars (aka. “Nebular Theory“) – a complete understanding of how these discs eventually become objects large enough to collapse under their own gravity has remained elusive.
Every now and then a scientific paper makes a real splash. We had one recently, to judge from recent headlines. “Moon rises to claim its place as a planet” said The Sunday Times on February 19, while the Mail Online asked “Is this lunarcy?”. The articles were among many responding to the humble paper: “A Geophysical Planet Definition”, which suggested that the criteria for determining what constitutes a planet need an overhaul. It argued that the moon, Pluto and several other bodies in the solar system should be upgraded to planets.
All seven planets discovered in orbit around the red dwarf star TRAPPIST-1 could easily fit inside the orbit of Mercury, the innermost planet of our solar system. In fact, they would have room to spare. TRAPPIST-1 also is only a fraction of the size of our sun; it isn't much larger than Jupiter. So the TRAPPIST-1 system's proportions look more like Jupiter and its moons than those of our solar system.
The search for life beyond Earth starts in habitable zones, the regions around stars where conditions could potentially allow liquid water – which is essential for life as we know it – to pool on a planet’s surface. New NASA research suggests some of these zones might not actually be able to support life due to frequent stellar eruptions – which spew huge amounts of stellar material and radiation out into space – from young red dwarf stars.
Humanity’s understanding of what constitutes a planet has changed over time. Whereas our most notable magi and scholars once believed that the world was a flat disc (or ziggurat, or cube), they gradually learned that it was in fact spherical. And by the modern era, they came to understand that the Earth was merely one of several planets in the known Universe.
On a clear night, and when light pollution isn’t a serious factor, looking up at the sky is a breathtaking experience. On occasions like these, it is easy to be blown away by the sheer number of stars out there. But of course, what we can see on any given night is merely a fraction of the number of stars that actually exist within our Galaxy.
Over the past two decades, we have surged into the exoplanet era. It was just 21 years ago that the discovery of the first planet orbiting a sun-like star was announced. Now, we know of 3,268 planets beyond the solar system, and new discoveries are announced every week. But how do we find these distant worlds? We’ve already described the two most successful methods used to date, known as the radial velocity and transit techniques.