cosmic seastar

  Most of the exoplanets we know of are either very large or orbit very close to their stars; like hot-Jupiters. But what about smaller planets that orbit very far from their stars? They’re rather a rarity. Why?  This JWST photo shows Uranus and its rings; Source: ESA It seems when it comes to planets, ice giants are often ignored. Despite their fascinating colors and far orbits that gives them their names, we don’t know a lot about the two planets farthest from the Sun: Uranus and Neptune.  It’s been nearly 40 years since a spacecraft first and last visited these two icy planets. I already wrote an article about why it’s so important to go back exploring them, and one of the reasons is: learning about Uranus and Neptune tells us a lot about exoplanets.  Among the most common sizes of exoplanets we know of are those intermediate in size between Earth and Neptune — based on their composition, they are either called super-Earths or mini-Neptunes. Sure, it’s entirely...

  It’s been almost 40 years since the last spacecraft landed on Venus. But why have been ignoring our Earth-sized neighbor for so long?  True color image of Venus; Source: Wikipedia There are three places in the Solar System that have received all the attention of scientists and engineers across the globe: Earth’s orbit, the Moon, and Mars. All three have a deep interconnectedness that lies in our very nature: Earth’s orbit is closest to home, the Moon protects us every night and controls the tides, and Mars has always been the curious red neighbor with seasons and Martian aliens who — at least in literature — go to war with Earthlings.  But while Mars is all the focus for crewed missions and extraterrestrial cities, it’s also fairly far away; on average 225 million km.  However, 40 million km from home lies another world — one that is almost as big as Earth with a thick atmosphere; a world closer to the Sun that interacts with the solar wind and thus offers the pl...

  In 2015, astronomers discovered the oldest planets so far: all of them are smaller than Earth and just two billion years younger than the universe itself. But could life even exist on such old planets? 11 billion years ago, the universe wasn’t as we know it today: stars bigger than any in our present-day universe lit up young galaxies still in the making. When our telescopes look back at this period of time, we find a chaotic universe — in crowded regions, three or more galaxies merge into larger ones, and the centers of young galaxies are defined by highly energetic quasars, active supermassive black holes.  It was also a time when the universe was strewn with much less heavy elements (anything heavier than helium), which are essential for life to develop. This means that there were much fewer terrestrial planets like our Earth — but they did exist.  Artist's impression of Methuselah orbiting its pulsar and white dwarf; Source: Wikipedia The oldest planet we know of...

  Every 80 years, faint T Coronae Borealis erupts to shine in bright magnitude 2, temporarily altering the night sky — and we have all signs that the system is about to burst again.  The constellation Corona Borealis where T CrB will erupt this year appears as in a crescent moon shape; Source: BBC Sky at Night In 2016, astronomers noticed something odd about the binary star system T Coronae Borealis (T CrB). The star is so faint it usually is only visible through a telescope; but that year, T CrB brightened by more than an entire magnitude from 10.5 to 9.2.  It was kind of a déjà-vu. In 1938, astronomers observed exactly the same brightening. And in 1946, the star erupted, glowing as bright as magnitude 2, equal in brightness to Polaris.  T CrB is the prime example of a recurrent nova — nova eruptions that seem to follow a strict cycle. Novae are different from supernovae in that they aren’t as energetic, and therefore don’t destroy the progenitor star.  In ...

  25 years since scientists discovered dark energy, we still have no clue what it exactly is. But as we learn more, it becomes clear that dark energy pretty much defines the future of the universe.  In the past five billion years, the expansion of the universe has accelerated; Source: Wikipedia The questions that bother astrophysicists for more than half a century: what is dark energy? Is it really dark? And why is it so difficult to find? All of these questions are easy and hard to answer at the same time. We know that dark energy drives the accelerated expansion of the universe that started about five billion years ago, around the same time the Sun was born.  Based on our theories, dark energy makes up 68% of the entire universe — so it’s really important that we understand what it is.  We may not have an idea what dark energy is exactly, but we have pretty sophisticated theories on how it affects the evolution of the universe.