Yes! Hubble is Back in Operation

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.

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How the Hubble Unlocked the Universe

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?

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Until We Get Another Mission at Saturn, We’re Going to Have to Make Do with these Pictures Taken by Hubble

This image of Saturn shows the planet and some of its moons in opposition. It's a composite image taken by the Hubble on June 6th, 2018. Image: NASA, ESA, A. Simon (GSFC) and the OPAL Team, and J. DePasquale (STScI); CC BY 4.0

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.

Continue reading “Until We Get Another Mission at Saturn, We’re Going to Have to Make Do with these Pictures Taken by Hubble”

This Beautiful Photo of Galaxy NGC 3981 was Taken by the Most Powerful Telescope in the World for no Scientific Reason at all. Just Because it’s Pretty

The world’s most powerful telescopes have a lot of work to do. They’re tasked with helping us unravel the mysteries of the universe, like dark matter and dark energy. They’re burdened with helping us find other habitable worlds that might host life. And they’re busy with a multitude of other tasks, like documenting the end of a star’s life, or keeping an eye on meteors that get too close to Earth.

But sometimes, they have to take a break.
Continue reading “This Beautiful Photo of Galaxy NGC 3981 was Taken by the Most Powerful Telescope in the World for no Scientific Reason at all. Just Because it’s Pretty”

170 Years Ago, Eta Carinae Erupted Dramatically. Astronomers Now Think They Know Why

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.

The studies which describe their findings – titled “Exceptionally fast ejecta seen in light echoes of Eta Carinae’s Great Eruption” and “Light echoes from the plateau in Eta Carinae’s Great Eruption reveal a two-stage shock-powered event” – recently appeared in the Monthly Notices of the Royal Astronomical Society.

Eta Carinae, one of the most massive stars known. Image credit: NASA
Eta Carinae, one of the most massive stars known and one of the brightest in the night sky. Credit: NASA

Both studies were led by Nathan Smith of the University of Arizona’s Steward Observatory, and included members from the Space Telescope Science Institute (STSI), the National Optical Astronomy Observatory (NOAO), the Millennium Institute of Astrophysics, the Harvard-Smithsonian Center for Astrophysics (CfA), the Cerro Tololo Inter-American Observatory and multiple universities.

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.

As Smith explained in a recent HubbleSite press release:

“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.”

The Homunculus Nebula, surrounding Eta Carinae. Credit: ESO, IDA, Danish 1.5 m, R. Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron

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.

Further Reading: HubbleSite, MNRAS, MNRAS (2)

New Photos of Saturn and Mars from Hubble

During the summer of 2018, the planets of Mars and Saturn (one after the other) have been in opposition. In astronomical terms, opposition refers to when a planet is on the opposite side of the Earth relative to the Sun. This not only means that the planet is closer to Earth in its respective orbit, but that is also fully lit by the Sun (as seen from Earth) and much more visible.

As a result, astronomers are able to observe these planets in greater detail. The Hubble Space Telescope took advantage of this situation to do what it has done best for the past twenty-eight years – capture some breathtaking images of both planets! Hubble made its observations of Saturn in June and Mars in July, and showed both planets close to their opposition.

Hubble’s high-resolution images of the planets and moons in our Solar System can only be surpassed by spacecraft that are either orbiting or conducting close flybys to them. However, Hubble has a major advantage over these types of missions, in that it can look at the Solar planets periodically and observe them over much longer periods of time than a passing spacecraft.

This composite image, taken by the NASA/ESA Hubble Space Telescope on June 6th, 2018, shows the ringed planet Saturn with six of its 62 known moons. Credit: NASA, ESA, A. Simon (GSFC) and the OPAL Team, and J. DePasquale (STScI)

Hubble observed Saturn on June 6th, almost a month before it reached opposition on June 27th. At the time, the ringed gas giant was approximately 1.4 billion km (870 million mi) from Earth. Hubble was able to capture the planet’s magnificent ring system at a time when it was at its maximum tilt to Earth, which allowed for a spectacular view of the rings and the gaps between them.

Hubble’s new image of Saturn also managed to capture the hexagonal storm around the gas giant’s north pole. This stable and persistent jet stream was first observed by the Voyager 1 probe during its flyby of Saturn in 1981, and has been a mystery to astronomers ever since. On top of that, the new image also features six of Saturn’s 62 known moons – Dione, Enceladus, Tethys, Janus, Epimetheus, and Mimas.

Hubble’s new image of Mars was captured on July 18th, 13 days before it reached its closest approach to Earth. This year will see the Red Planet get as close as 57.6 million km from Earth, which is the closest approach made since 2003. On that occasion, Mars was just 55,757,930 km (34,647,420 mi) from Earth, which was the closest the planet had been to Earth in almost 60,000 years!

Mars is at opposition to Earth every two years, so Hubble has had many opportunities to capture detailed images of the planet’s surface. However, this new image is different in that it is dominated by a gigantic sandstorm that is currently encompassing the entire planet. This storm has been raging since May of 2018 and developed into a planet-wide dust storm within several weeks.

In mid-July the NASA/ESA Hubble Space Telescope observed Mars, only 13 days before the planet made its closest approach to Earth in 2018. Credit: NASA, ESA, and STScI

Dust storms are a common occurrence on Mars. They take place every year, usually stay contained to a local area, and normally last only about a few weeks. Larger dust storms that can grow to cover the entire planet are a rarer event, and can typically last for weeks or even months. These tend to happen during the spring and summer months in the southern hemisphere, which coincides with Mars being closer to the Sun in its elliptical orbit.

Due to increased temperatures, dust particles are lifted higher into the atmosphere, creating more wind. The resulting wind kicks up yet more dust, creating a feedback loop that NASA scientists are still trying to understand. While spacecraft orbiting Mars and rovers and lander can study storm behavior at lower altitudes or from the surface, Hubble observations allow astronomers to study changes in the higher atmosphere.

The combined observations will help planetary scientists to better understanding how these global storms arise. Despite the obscuring dust storm, Hubble still managed to capture several important Martian surface features like the polar ice caps, Terra Meridiani, the Schiaparelli Crater, and Hellas Basin – even though all of them appear slightly blurred in the image.

The Hellas Basin – an impact basin that measures 2200 km (1367 mi) across and is nearly 8 km (4.97 mi) deep – is visible at the lower right and appears as a large and bright oval area. The orange area in the upper center of the image is Arabia Terra, a large upland area in northern Mars. This region is characterized by many impact craters and heavy erosion, which indicates that it could be among the oldest terrains on the planet.

This annotated image of Mars shows features of the planet that were visible in summer 2018 despite a global dust storm. Credit: NASA, ESA, and STScI

South of Arabia Terra are the dark streaks known as Sinus Sabaeus and Sinus Meridiani, features that stretch from east to west along the equator and are made of up dark bedrock and sand deposits from ancient lava flows. Because it was autumn in the northern hemisphere when the image was taken, it is covered in a bright blanket of clouds – and clouds can also be seen above the northern and southern polar ice caps. Last, but not least, Mars’ two small moons – Phobos and Deimos – appear in the lower half of the image.

Comparing these new images of Mars and Saturn with older data gathered by Hubble, other telescopes and the many probes that have taken images of them over the years will allow astronomers to study how cloud patterns and large-scale structures on the Solar planets change over time. These latest images also show that even after almost three decades of being in operation, Hubble is still able to pull its weight!

And be sure to enjoy this video about the images acquired by Hubble, courtesy of Hubblecast:

Further Reading: Hubble

This is a Photo of Neptune, From the Ground! ESO’s New Adaptive Optics Makes Ground Telescopes Ignore the Earth’s Atmosphere

In 2007, the European Southern Observatory (ESO) completed work on the Very Large Telescope (VLT) at the Paranal Observatory in northern Chile. This ground-based telescope is the world’s most advanced optical instrument, consisting of four Unit Telescopes with main mirrors (measuring 8.2 meters in diameter) and four movable 1.8-meter diameter Auxiliary Telescopes.

Recently, the VLT was upgraded with a new instrument known as the Multi Unit Spectroscopic Explorer (MUSE), a panoramic integral-field spectrograph that works at visible wavelengths. Thanks to the new adaptive optics mode that this allows for (known as laser tomography) the VLT was able to recently acquire some images of Neptune, star clusters and other astronomical objects with impeccable clarity.

In astronomy, adaptive optics refers to a technique where instruments are able to compensate for the blurring effect caused by Earth’s atmosphere, which is a serious issue when it comes to ground-based telescopes. Basically, as light passes through our atmosphere, it becomes distorted and causes distant objects to become blurred (which is why stars appear to twinkle when seen with the naked eye).

Images of the planet Neptune obtained during the testing of the Narrow-Field adaptive optics mode of the MUSE/GALACSI instrument on ESO’s Very Large Telescope. Credit: ESO/P. Weilbacher (AIP

One solution to this problem is to deploy telescopes into space, where atmospheric disturbance is not an issue. Another is to rely on advanced technology that can artificially correct for the distortions, thus resulting in much clearer images. One such technology is the MUSE instrument, which works with an adaptive optics unit called a GALACSI – a subsystem of the Adaptive Optics Facility (AOF).

The instrument allows for two adaptive optics modes – the Wide Field Mode and the Narrow Field Mode. Whereas the former corrects for the effects of atmospheric turbulence up to one km above the telescope over a comparatively wide field of view, the Narrow Field mode uses laser tomography to correct for almost all of the atmospheric turbulence above the telescope to create much sharper images, but over a smaller region of the sky.

This consists of four lasers that are fixed to the fourth Unit Telescope (UT4) beaming intense orange light into the sky, simulating sodium atoms high in the atmosphere and creating artificial “Laser Guide Stars”. Light from these artificial stars is then used to determine the turbulence in the atmosphere and calculate corrections, which are then sent to the deformable secondary mirror of the UT4 to correct for the distorted light.

Using this Narrow Field Mode, the VLT was able to capture remarkably sharp test images of the planet Neptune, distant star clusters (such as the globular star cluster NGC 6388), and other objects. In so doing, the VLT demonstrated that its UT4 mirror is able to reach the theoretical limit of image sharpness and is no longer limited by the effects of atmospheric distortion.

The most powerful laser guide star system in the world sees first light at the Paranal Observatory. Credit: ESO

This essentially means that it is now possible for the VLT to capture images from the ground that are sharper than those taken by the Hubble Space Telescope. The results from UT4 will also help engineers to make similar adaptations to the ESO’s Extremely Large Telescope (ELT), which will also rely on laser tomography to conduct its surveys and accomplish its scientific goals.

These goals include the study of supermassive black holes (SMBHs) at the centers of distant galaxies, jets from young stars, globular clusters, supernovae, the planets and moons of the Solar System, and extra-solar planets. In short, the use of adaptive optics – as tested and confirmed by the VLT’s MUSE – will allow astronomers to use ground-based telescopes to study the properties of astronomical objects in much greater detail than ever before.

In addition, other adaptive optics systems will benefit from work with the Adaptive Optics Facility (AOF) in the coming years. These include the ESO’s GRAAL, a ground layer adaptive optics module that is already being used by  the Hawk-I infrared wide-field imager. In a few years, the powerful Enhanced Resolution Imager and Spectrograph (ERIS) instrument will also be added to the VLT.

Between these upgrades and the deployment of next-generation space telescopes in the coming years (like the James Webb Space Telescope, which will be deploying in 2021), astronomers expect to bringing a great deal more of the Universe “into focus”. And what they see is sure to help resolve some long-standing mysteries, and will probably create a whole lot more!

And be sure to enjoy these videos of the images obtained by the VLT of Neptune and NGC 6388, courtesy of the ESO:

Further Reading: ESO

Good News, James Webb is Still a Go. Bad News, Launching in 2021

When it is deployed to space, the James Webb Space Telescope (JWST) will be the most powerful and advanced telescope ever deployed. As the spiritual and scientific successor to the Hubble, Spitzer, and Kepler Space Telescopes, this space observatory will use its advanced suite of infrared instruments to look back at the early Universe, study the Solar System, and help characterize extra-solar planets.

Unfortunately, after many delays, there’s some good news and bad news about this mission. The good news is that recently, the Independent Review Board (IRB) established by NASA to assess the progress on the JWST unanimously decided that work on the space telescope should continue. The bad news is that NASA has decided to push the launch date back again – this time to March 30th, 2021.

As part of their assessment, the IRB was established in April of 2018 to address a range of factors influencing Webb’s schedule and performance. These included the technical challenges and tasks that need to be tackled by its primary contractor (Northrop Grumman) before the mission can launch. A summary of the report’s recommendations, and NASA’s response, can be read here.

The Hubble Space Telescope on the left has a 2.4 meter mirror and the James Webb Space Telescope has a 6.5 meter mirror. LUVOIR, not shown, will dwarf them both with a massive 15 meter mirror. Image: NASA
The Hubble Space Telescope on the left has a 2.4 meter mirror and the James Webb Space Telescope has a 6.5 meter mirror. LUVOIR, not shown, will dwarf them both with a massive 15 meter mirror. Credit: NASA

In the report, the IRB identified technical issues, which including human errors, that they claim have greatly impacted the development schedule. As they stated in their Overview:

“The observation that there are no small JWST integration and test problems was not initially recognized by the Webb IRB, and this also may be true of others involved with JWST. It is a most important observation that will be apparent in subsequent Findings and Recommendations. It is caused by the complexity and highly integrated nature of the observatory. Specifically, it implies, as an example, that a very small human error or test anomaly can impact the schedule by months and the cost by tens of millions of dollars.”

The anomaly mentioned in the report refers to the “anomalous readings” that were detected from the telescope during vibration testing back in December 2016. NASA responded to this by giving the project up to 4 months of schedule reserve by extending the launch window. However, in 2017, NASA delayed the launch window again by 5 months, from October 2018 to a between March and June 2019.

This delay was requested by the project team, who indicated that they needed to address lessons learned from the initial folding and deployment of the observatory’s sun shield. In February of 2018, the Government Accountability Office (GAO) issued a report that expressed concerns over further delays and cost overruns. Shortly thereafter, the JWST’s Standing Review Board (SRB) made an independent assessment of the remaining tasks.

The James Webb Space Telescope being placed in the Johnson Space Center’s historic Chamber A on June 20th, 2017. Credit: NASA/JSC

In May of 2018, NASA issued a statement indicating that they now estimated that the launch window would be some time in May 2020. However, they chose to await the findings of the IRB and consider the data from the JWST’s Standing Review Board before making the final determination. The new launch date was set to accommodate environmental testing and work performances challenges on the sunshield and propulsion system.

According to the IRB report, this latest delay will also result in a budget overrun. “As a result of the delay, Webb’s total lifecycle cost to support the March 2021 launch date is estimated at $9.66 billion,” they concluded. “The development cost estimate to support the new launch date is $8.8B (up from the $8B development cost estimate established in 2011).”

As Jim Bridenstine, the NASA Administrator, indicated in a message to the NASA workforce on Wednesday about the report:

“Webb is vital to the next generation of research beyond NASA’s Hubble Space Telescope. It’s going to do amazing things – things we’ve never been able to do before – as we peer into other galaxies and see light from the very dawn of time. Despite major challenges, the board and NASA unanimously agree that Webb will achieve mission success with the implementation of the board’s recommendations, many of which already are underway.”

In the end, the IRB, SRB and NASA are all in total agreement that the James Webb Space Telescope is a crucial mission that must be seen through. In addition to shedding light on a number of mysteries of the Universe – ranging from the earliest stars and galaxies in the Universe to exoplanet habitability – the JWST will also complement and enhance the discoveries made by other missions.

The combined optics and science instruments of NASA’s James Webb Space Telescope being removed from the Space Telescope Transporter for Air, Road and Sea (STTARS) at the Northrop Grumman company headquarters on March 8th, 2018. Credits: NASA/Chris Gunn

These include not only Hubble and Spitzer, but also missions like the Transiting Exoplanet Survey Satellite (TESS), which launched this past April. Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, also issued a statement on the recent report:

“The more we learn more about our universe, the more we realize that Webb is critical to answering questions we didn’t even know how to ask when the spacecraft was first designed. Webb is poised to answer those questions, and is worth the wait. The valuable recommendations of the IRB support our efforts towards mission success; we expect spectacular scientific advances from NASA’s highest science priority.”

The JWST will also be the first telescope of its kind, being larger and more complex than any previous space telescope – so challenges were anticipated from its very inception. In addition, the final phase consists of some of the most challenging work, where the 6.5-meter telescope and science payload element are being joined with the spacecraft element to complete the observatory.

The science team also needs to ensure that the observatory can be folded up to fit inside the Ariane 5 rocket that will launch it into space. They also need to ensure that it will unfold again once it reaches space, deploy its sunshield, mirrors and primary mirror. Beyond that, there are also the technical challenges of building a complex observatory that was created here on Earth, but designed to operate in space.

As a collaborative project between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), the JWST is also representative of the new era of international cooperation. As such, no one wishes to see the mission abandoned so close to completion. In the meantime, any delays that allow for extra testing will only ensure success in the long run.

Good luck JWST, we look forward to hearing about your first discoveries!

Further Reading: NASA

A Long Exposure Hubble Image of a Galaxy Cluster Also Turned up 22 Asteroids

The Hubble Space Telescope is the oldest space telescope in operation, having spent the past twenty-eight years in orbit. Nevertheless, this mission is still hard at work revealing things about our Solar System, neighboring exoplanets, and some of the farthest reaches of the Universe. And every so often, it also captures an image that happens to turn up something interesting and unexpected.

Recently, while conducting a study of Abell 370, a galaxy cluster located approximately four billion light-years away in the constellation Cetus (the Sea Monster), Hubble managed to spot something in foreground. While observing this collection of several hundred galaxiess, the image was photobombed by 22 asteroids whose tails created streaks that looked like background astronomical phenomena.

The study was part of the Frontier Fields program, where Hubble has captured images of some of the earliest galaxies in the Universe (aka. “relic galaxies”) in order to determine how it evolved over time. The position of this asteroid field is near the ecliptic (the plane of our Solar System) where most asteroids reside, which is why Hubble astronomers saw so many crossings.

Artist’s impression of a Near-Earth Asteroid passing by Earth. Credit: ESA

In the past, Hubble has recorded many instances of asteroid trails when conducting observations along a line-of-sight near the plane of our Solar System. In this case, the Near-Earth Asteroids (NEAs) – which orbit Earth at an average distance of about 260 million km (161.5 million mi) – were previously undetected due to their faintness. But thanks to the images taken by Hubble, scientists were able to identify them manually based on their motion.

Of the 22 asteroids, five were identified as unique objects. The image was assembled from several exposures taken in visible and infrared light, which was first released on November 6th, 2017. The image was prepared in honor of “Asteroid Day”, a global annual event that takes place every June 30th to raise awareness about asteroids and what can be done to protect Earth from a possible impact.

The day falls on the anniversary of the Tunguska event, which took place on June 30th, 1918, in eastern Russia and resulted in the flattening of 2,000 square km (770 square mi) of forest. While far less harmful than the Cretaceous–Paleogene (K–Pg) extinction event – which took place 66 million years ago and is believed to have killed the dinosaurs – Tunguska was the most harmful asteroid event in recorded history.

In many of the images snapped by Hubble, the asteroid tails appeared as white trails that look like curved streaks, an effect caused by parallax. In astronomy, parallax is an observational effect where the apparent position of an object appears to be different based on different lines of sight. Basically, as Hubble orbited around the Earth and took several images of the galaxy, the asteroids appeared to be moving relative to the background stars and galaxies.

The massive galaxy cluster Abell 370 as seen by Hubble Space Telescope in the final Frontier Fields observations. Credit: NASA/ESA/HFF

The asteroids own motion along their orbits and other contributing factors also led to their streaked appearance. Whereas the white streaks were identified as asteroid tails, the blue streaks are distorted images of distant galaxies behind the cluster. This effect is known as gravitational lensing, where light from distant objects is warped and magnified by the presence of an intervening object.

In this case, the intervening object who’s gravitational force magnified the light of the background galaxies was Abell 370. These more distant galaxies are too distant for Hubble to see directly, hence why astronomers use the technique to study the most distant objects in the Universe. But whereas the blue streaks were expected, the white streaks caused by asteroids took scientists completely by surprise!

This year, the European Space Agency (ESA) is co-hosting a live webcast with the European Southern Observatory (ESO) with expert interviews, news on some the most recent asteroid research, and a discussion about what killed the dinosaurs. You can watch this event tomorrow starting at 13:00 CEST (11:00 UST/04:00 PST) by going to the ESA’s Asteroid Day web page.

Further Reading: ESA

The Universe’s Missing Matter. Found!

In the 1960s, astronomers began to notice that the Universe appeared to be missing some mass. Between ongoing observations of the cosmos and the the Theory of General Relativity, they determined that a great deal of the mass in the Universe had to be invisible. But even after the inclusion of this “dark matter”, astronomers could still only account for about two-thirds of all the visible (aka. baryonic) matter.

This gave rise to what astrophysicists dubbed the “missing baryon problem”. But at long last, scientists have found what may very well be the last missing normal matter in the Universe. According to a recent study by a team of international scientists, this missing matter consists of filaments of highly-ionized oxygen gas that lies in the space between galaxies.

The study, titled “Observations of the missing baryons in the warm–hot intergalactic medium“, recently appeared in the scientific journal Nature. The study was led by Fabrizio Nicastro, a researcher from the Istituto Nazionale di Astrofisica (INAF) in Rome, and included members from the SRON Netherlands Institute for Space Research, the Harvard–Smithsonian Center for Astrophysics (CfA), the Instituto de Astronomia Universidad Nacional Autonoma de Mexico, the Instituto Nacional de Astrofísica, Óptica y Electrónica, the Instituto de Astrofísica de La Plata (IALP-UNLP) and multiple universities.

Artist’s impression of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun. Credit: ESO/M. Kornmesser

For the sake of their study, the team consulted data from a series of instruments to examine the space near a quasar called 1ES 1553. Quasars are extremely massive galaxies with Active Galactic Nuclei (AGN) that emit tremendous amounts of energy. This energy is the result of gas and dust being accreted onto supermassive black holes (SMBHs) at the center of their galaxies, which results in the black holes emitting radiation and jets of superheated particles.

In the past, researchers believed that of the normal matter in the Universe, roughly 10% was bound up in galaxies while 60% existed in diffuse clouds of gas that fill the vast spaces between galaxies. However, this still left 30% of normal matter unaccounted for. This study, which was the culmination of a 20-year search, sought to determine if the last baryons could also be found in intergalactic space.

This theory was suggested by Charles Danforth, a research associate at CU Boulder and a co-author on this study, in a 2012 paper that appeared in The Astrophysical Journal – titled “The Baryon Census in a Multiphase Intergalactic Medium: 30% of the Baryons May Still be Missing“. In it, Danforth suggested that the missing baryons were likely to be found in the warm-hot intergalactic medium (WHIM), a web-like pattern in space that exists between galaxies.

As Michael Shull – a professor of Astrophysical and Planetary Sciences at the University of Colorado Boulder and one of the co-authors on the study – indicated, this wild terrain seemed like the perfect place to look.“This is where nature has become very perverse,” he said. “This intergalactic medium contains filaments of gas at temperatures from a few thousand degrees to a few million degrees.”

Close-up of star near a supermassive black hole (artist’s impression). Credit: ESA/Hubble, ESO, M. Kornmesser

To test this theory, the team used data from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope to examine the WHIM near the quasar 1ES 1553. They then used the European Space Agency’s (ESA) X-ray Multi-Mirror Mission (XMM-Newton) to look closer for signs of the baryons, which appeared in the form of highly-ionized jets of oxygen gas heated to temperatures of about 1 million °C (1.8 million °F).

First, the researchers used the COS on the Hubble Space Telescope to get an idea of where they might find the missing baryons in the WHIM. Next, they homed in on those baryons using the XMM-Newton satellite. At the densities they recorded, the team concluded that when extrapolated to the entire Universe, this super-ionized oxygen gas could account for the last 30% of ordinary matter.

As Prof. Shull indicated, these results not only solve the mystery of the missing baryons but could also shed light on how the Universe began. “This is one of the key pillars of testing the Big Bang theory: figuring out the baryon census of hydrogen and helium and everything else in the periodic table,” he said.

Looking ahead, Shull indicated that the researchers hope to confirm their findings by studying more bright quasars. Shull and Danforth will also explore how the oxygen gas got to these regions of intergalactic space, though they suspect that it was blown there over the course of billions of years from galaxies and quasars. In the meantime, however, how the “missing matter” became part of the WHIM remains an open question. As Danforth asked:

“How does it get from the stars and the galaxies all the way out here into intergalactic space?. There’s some sort of ecology going on between the two regions, and the details of that are poorly understood.”

Assuming these results are correct, scientists can now move forward with models of cosmology where all the necessary “normal matter” is accounted for, which will put us a step closer to understanding how the Universe formed and evolved. Now if we could just find that elusive dark matter and dark energy, we’d have a complete picture of the Universe! Ah well, one mystery at a time…

Further Reading: UCB, Nature