Like Earth, Uranus and Neptune have season and experience changes in weather patterns as a result. But unlike Earth, the seasons on these planets last for years rather than months, and weather patterns occur on a scale that is unimaginable by Earth standards. A good example is the storms that have been observed in Neptune and Uranus’ atmosphere, which include Neptune’s famous Great Dark Spot.
During its yearly routine of monitoring Uranus and Neptune, NASA’s Hubble Space Telescope (HST) recently provided updated observations of both planets’ weather patterns. In addition to spotting a new and mysterious storm on Neptune, Hubble provided a fresh look at a long-lived storm around Uranus’ north pole. These observations are part of Hubble‘s long-term mission to improve our understanding of the outer planets.
It allowed us to spot auroras on Saturn and planets orbiting distant suns. It permitted astronomers to see galaxies in the early stages of formation, and look back to some of the earliest periods in the Universe. It also measured the distances to Cepheid variable stars more accurately than ever before, which helped astrophysicists constrain how fast the Universe is expanding (the Hubble Constant).
It did all of this and more, which is why no space telescope is as recognized and revered as the Hubble Space Telescope. And while it’s mission is currently scheduled to end in 2021, Hubble is still breaking new ground. Thanks to the efforts of a research team from the Instituto de Astrofísica de Canarias (IAC), Hubble recently obtained the deepest images of the Universe ever taken from space.
How fast is the Universe expanding? That’s a question that astronomers haven’t been able to answer accurately. They have a name for the expansion rate of the Universe: The Hubble Constant, or Hubble’s Law. But measurements keep coming up with different values, and astronomers have been debating back and forth on this issue for decades.
The basic idea behind measuring the Hubble Constant is to look at distant light sources, usually a type of supernovae or variable stars referred to as ‘standard candles,’ and to measure the red-shift of their light. But no matter how astronomers do it, they can’t come up with an agreed upon value, only a range of values. A new study involving quasars and gravitational lensing might help settle the issue.
On January 8th, an important piece of equipment on the Hubble Space Telescope went down. The Wide Field Camera 3 (WFC3) suspended its operations because of a hardware. The Hubble team is investigating the anomaly, and during this time the space telescope’s other instruments are working normally and continuing their science operations.
The WFC3 was installed on the Hubble in 2009. It replaced the Wide Field and Planetary Camera 2 (WFPC2). The WFC3 is the most technologically advanced instrument on the Hubble, and it has captured some of the most stunning and famous images ever captured.
To the unaided eye, the Triangulum Galaxy is just a smudge in the night sky. But it’s a smudge that contains about 40 billion stars. It also contains some very active star-forming regions, which have attracted the eyes of astronomers.
The Triangulum has a couple other names: Messier 33 and NGC 598. But Triangulum is the easier name to remember. (It’s also sometimes called the “Pinwheel Galaxy.”) But whatever name you choose to call it, this Hubble image brings it to life.
Since it was first launched into space in 1990, the Hubble Space Telescope has become something of a household name. Over the course of its almost thirty years of service, Hubble has established a reputation as one of NASA’s Great Observatories, giving astronomers the ability to look farther into the cosmic field than ever before and learn new and fascinating things about our Universe.
It was therefore a bit of a scare then when NASA announced earlier this month that one of Hubble’s gyroscopes (gyros) had failed, causing it to go into safe mode. But on Oct. 26th, after a considerable effort on behalf of the operations team, NASA announced that the venerable Hubble had been restored to working order. As we speak, it is collecting science data and carrying on in the tradition it helped establish.
As engineers and technicians work diligently to diagnose and develop a solution (at best) or work around (at worst) the recent gyroscope issues in the Hubble Space Telescope, it gives us a moment to check in and reflect on some of its greatest feats of science. Don’t worry, that great observatory in the sky isn’t going anywhere anytime soon (as much as we would like an upgrade or replacement), so we can confidently look forward to many more years of astronomical greatness. But the Hubble has been running for almost three decades now; what has it contributed to the sum total of human knowledge of the universe?
We can’t seem to get enough of Saturn. It’s the most visually distinct object in our Solar System (other than the Sun, of course, but it’s kind of hard to gaze at). The Cassini mission to Saturn wrapped up about a year ago, and since then we’re relying on the venerable Hubble telescope to satisfy our appetite for images of the ringed planet.
Eta Carinae, a double star system located 7,500 light years away in the constellation Carina, has a combined luminosity of more than 5 million Suns – making it one of the brightest stars in the Milky Way galaxy. But 170 years ago, between 1837 and 1858, this star erupted in what appeared to be a massive supernova, temporarily making it the second brightest star in the sky.
Strangely, this blast was not enough to obliterate the star system, which left astronomers wondering what could account for the massive eruption. Thanks to new data, which was the result of some “forensic astronomy” (where leftover light from the explosion was examined after it reflected off of interstellar dust) a team of astronomers now think they have an explanation for what happened.
In their first study, the team indicates how they studied the “light echoes” produced by the explosion, which were reflected off of interstellar dust and are just now visible from Earth. From this, they observed that the eruption resulted in material expanding at speeds that were up to 20 times faster than with any previously-observed supernova.
In the second study, the team studied the evolution of the echo’s light curve, which revealed that it experienced spikes before 1845, then plateaued until 1858 before steadily declining over the next decade. Basically, the observed velocities and light curve were consistent with the blast wave of a supernova explosion rather than the relatively slow and gentle winds expected from massive stars before they die.
The light echoes were first detected in images obtained in 2003 by telescopes at the Cerro Tololo Inter-American Observatory in Chile. For the sake of their study, the team consulted spectroscopic data from the Magellan telescopes at the Las Campanas Observatory and the Gemini South Observatory, both located in Chile. This allowed the team to measure the light and determine the ejecta’s expansion speeds – more than 32 million km/h (20 million mph).
Based on this data, the team hypothesized that the eruption may have been triggered by a prolonged battle between three stars, which destroyed one star and left the other two in a binary system. This battle may have culminated with a violent explosion when Eta Carinae devoured one of its two companions, sending more than 10 Solar masses into space. This ejected mass created the gigantic bipolar nebula (aka. “the Homunculus Nebula”) which is seen today.
“We see these really high velocities in a star that seems to have had a powerful explosion, but somehow the star survived. The easiest way to do this is with a shock wave that exits the star and accelerates material to very high speeds.”
In this scenario, Eta Carinae started out as a trinary system, with two massive stars orbiting close to each other and the third orbiting further away. When the most massive of the binary neared the end of its life, it began to expand and then transfer much of its material onto its slightly smaller companion. This caused the smaller star to accumulate just enough energy to cause it to eject its outer layers, but not enough to completely annihilate it.
The companion star would have then grown to become about 100 times the mass of our Sun and extremely bright. The other star, now weighing only 30 Solar masses, would have been stripped of its hydrogen layers, exposing its hot helium core – which represent an advanced stage of evolution in the lives of massive stars. As Armin Rest – a researcher from the STSI, The John Hopkins University and a co-author on the paper – explained:
“From stellar evolution, there’s a pretty firm understanding that more massive stars live their lives more quickly and less massive stars have longer lifetimes. So the hot companion star seems to be further along in its evolution, even though it is now a much less massive star than the one it is orbiting. That doesn’t make sense without a transfer of mass.”
This transfer of mass would have altered the gravitational balance of the system, causing the helium-core star to move farther away from its now-massive companion and eventually travel so far that it would interact with the outermost third star. This would cause the third star to move towards the massive star and eventually merge with it, producing an outflow of material.
Initially, the merger caused ejecta that expanded relatively slowly, but as the two stars finally joined together, they produced an explosive event that blasted material off 100 times faster. This material caught up to the slow ejecta, pushing it forward and heating the material until it glowed. This glowing material was the main light source that was viewed by astronomers 170 years ago.
In the end, the smaller helium-core star settled into an elliptical orbit around around its massive counterpart, passing through the star’s outer layers every 5.5 years and generating X-ray shock waves. According to Smith, while this explanation cannot account for everything observed in Eta Carinae, it does explain both the brightening and the fact that the star remains:
“The reason why we suggest that members of a crazy triple system interact with each other is because this is the best explanation for how the present-day companion quickly lost its outer layers before its more massive sibling.”
These studies have provided new clues as to the mystery of how Eta Carinae appeared to explode in a massive supernova, but left behind a massive star and nebula. In addition, a better understanding of the physics behind the Eta Carinae explosion could help astronomers to learn more about the complicated interactions that govern binary and multiple star systems – which are critical to our understanding of the evolution and death of massive stars.