It’s been almost 19 years since I founded Universe Today, back in March, 1999.
Back when I started, it was a primarily an email-based newsletter with an archive version on the web where people could read it if they wanted to.
The technology was pretty rudimentary at the time, so I had to do everything by hand, sending out a BCC email to thousands of people every day, eventually finding other email mailing list providers. At some point, I shifted from commentary and summaries to full on reporting on space news. And at that time, automated tools arrived that would take all the stories you wrote in a day, bundled them up and sent them out via email to a list of subscribers.
That was great and convenient for me, but it didn’t make for the best experience. It lost its soul.
A couple of months ago, I decided to return to my roots and continue maintaining a weekly email newsletter that summarizes some of the top stories that happened this week. And not just stories from here on Universe Today, but stories from across the Universe of space journalists and websites, including Space.com, Ars Technica, Ethan Siegel, Brian Koberlein, TheVerge and many more. I see more amazing things out there than we could ever report on. I figured I might as well share it.
Each edition of the weekly newsletter comes out on Friday, and is hand-written personally by me, and includes a few dozen summaries and links to stories on Universe Today and beyond, as well as cool pictures, videos, and astrophotography.
It’s SPAM free, I won’t sell the email addresses to anyone. There aren’t any ads in them, although I’ll occasionally promote books, trips and other projects I’m working on, but tastefully, I promise.
Jupiter's prominent storm, the Great Red Spot, is held in place by the alternating storm bands in Jupiter's atmosphere. Image: By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons
Back in the late 1980’s, Voyager 2 was the first spacecraft to capture images of the giant storms in Neptune’s atmosphere. Before then, little was known about the deep winds cycling through Neptune’s atmosphere. But Hubble has been turning its sharp eye towards Neptune over the years to study these storms, and over the past couple of years, it’s watched one enormous storm petering out of existence.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect.” – Michael H. Wong, University of California at Berkeley.
When we think of storms on the other planets in our Solar System, we automatically think of Jupiter. Jupiter’s Great Red Spot is a fixture in our Solar System, and has lasted 200 years or more. But the storms on Neptune are different: they’re transient.
Voyager 2 captured this image of Neptune in 1982, when it was over 7 million km (4.4 million miles) away from the planet. The Great Dark Spot in the middle of the image was the first storm ever seen on Neptune. Image: By NASA (JPL image) [Public domain], via Wikimedia Commons
The storm on Neptune moves in an anti-cyclonic direction, and if it were on Earth, it would span from Boston to Portugal. Neptune has a much deeper atmosphere than Earth—in fact it’s all atmosphere—and this storm brings up material from deep inside. This gives scientists a chance to study the depths of Neptune’s atmosphere without sending a spacecraft there.
The first question facing scientists is ‘What is the storm made of?’ The best candidate is a chemical called hydrogen sulfide (H2S). H2S is a toxic chemical that stinks like rotten eggs. But particles of H2S are not actually dark, they’re reflective. Joshua Tollefson from the University of California at Berkeley, explains: “The particles themselves are still highly reflective; they are just slightly darker than the particles in the surrounding atmosphere.”
“We have no evidence of how these vortices are formed or how fast they rotate.” – Agustín Sánchez-Lavega, University of the Basque Country in Spain.
But beyond guessing what chemical the spot might me made of, scientists don’t know much else. “We have no evidence of how these vortices are formed or how fast they rotate,” said Agustín Sánchez-Lavega from the University of the Basque Country in Spain. “It is most likely that they arise from an instability in the sheared eastward and westward winds.”
There’ve been predictions about how storms on Neptune should behave, based on work done in the past. The expectation was that storms like this would drift toward the equator, then break up in a burst of activity. But this dark storm is on its own path, and is defying expectations.
“We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity.” – Michael H. Wong, University of California at Berkeley.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect,” said Michael H. Wong of the University of California at Berkeley, referring to work by Ray LeBeau (now at St. Louis University) and Tim Dowling’s team at the University of Louisville. “Their dynamical simulations said that anticyclones under Neptune’s wind shear would probably drift toward the equator. We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity.”
Rather than going out in some kind of notable burst of activity, this storm is just fading away. And it’s also not drifting toward the equator as expected, but is making its way toward the south pole. Again, the inevitable comparison is with Jupiter’s Great Red Spot (GRS).
The GRS is held in place by the prominent storm bands in Jupiter’s atmosphere. And those bands move in alternating directions, constraining the movement of the GRS. Neptune doesn’t have those bands, so it’s thought that storms on Neptune would tend to drift to the equator, rather than toward the south pole.
Jupiter’s prominent storm, the Great Red Spot, is held in place by the alternating storm bands in Jupiter’s atmosphere. Image: By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons
This isn’t the first time that Hubble has been keeping an eye on Neptune’s storms. The Space Telescope has also looked at storms on Neptune in 1994 and 1996. The video below tells the story of Hubble’s storm watching mission.
The images of Neptune’s storms are from the Hubble Outer Planets Atmosphere Legacy (OPAL) program. OPAL gathers long-term baseline images of the outer planets to help us understand the evolution and atmospheres of the gas giants. Images of Jupiter, Saturn, Uranus and Neptune are being taken with a variety of filters to form a kind of time-lapse database of atmospheric activity on the four gas planets.
To celebrate the launch of the Falcon Heavy, we figured it was time for an all new series, this time on the rockets that carry us to space. Today we’re going to talk about why single stage to orbit rockets are so difficult to carry out.
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
Welcome to the 549th Carnival of Space! The Carnival is a community of space science and astronomy writers and bloggers, who submit their best work each week for your benefit. So now, on to this week’s stories! Continue reading “Carnival of Space #549”
Andromeda Galaxy. Credit: Wikipedia Commons/Adam Evans
Since ancient times, astronomers have looked up at the night sky and seen the Andromeda galaxy. As the closest galaxy to our own, scientists have been able to observe and scrutinize this giant spiral galaxy for millennia. By the 20th century, astronomers realized that Andromeda was the Milky Way’s sister galaxy and was moving towards us. In 4.5 billion years, it will even merge with our own to form a supergalaxy.
However, it seems astronomers were wrong about the Andromeda galaxy in one major respect. According to recent study led by a team of French and Chinese astronomers, this giant spiral galaxy formed from a major merger that occurred less than 3 billion years ago. This means that Andromeda, as we know it today, is effectively younger than our very own Solar System, which has it beat by about 1.5 billion years!
For the sake of their study, the relied on data gathered by recent surveys that noted considerable differences between the Andromeda and Milky Way galaxies. The first of these studies, which took place between 2006 and 2014, demonstrated all Andromeda has a wealth of young blue stars in its disk (less than 2 billion years old) that undergo random motions over large scales. This is contrast to the stars in the Milky Way’s disk, which are subject only to simple rotation.
In addition, deep observations conducted between 2008 and 2014 with the French-Canadian telescope in the Hawaiian Islands (CFHT) indicated some interesting things about Andromeda’s halo. This vast region, which is 10 times the size of the galaxy itself, is populated by gigantic currents of stars. The most prominent of which is called the “Giant Stream”, a warped disk that has shells and clumps at its very edges.
Using this data, the French-Chinese collaboration then created a detailed numerical model of Andromeda using the two most powerful computers available in France – the Paris Observatory’s MesoPSL and the National Center for Scientific Research’s (CNRS) IDRIS-GENCI supercomputer. With the resulting numerical model, the team was able to demonstrate that these recent observations could be explained only by a recent collision.
Basically, they concluded that between 7 and 10 billion years ago, Andromeda consisted of two galaxies that had slowly achieved a encountering orbit. After optimizing the trajectories of both galaxies, they determined that they would have collided 1.8 to 3 billion years ago. This collision is what gave birth to Andromeda as we know it today, which effectively makes it younger than our Solar System – which formed almost 4.6 billion years ago.
What’s more, they were able to calculate mass distributions for both parent galaxies that merged to formed Andromeda, which indicated that the larger galaxy was four times the size of the smaller. But most importantly, the team was able to reproduce in detail all the structures that compose Andromeda today – including the bulge, the bar, the huge disk, and the presence of young stars.
The presence of young blue stars in its disk, which has remained unexplained until now, is attributable to a period of intense star formation that took place after the collision. In addition, structures like the “Giant Stream” and the shells of the halo belonged to the smaller parent galaxy, whereas the diffuse clumps and the warped nature of the halo were derived from the larger one.
Their study also explains why the features attributed to the smaller galaxy have an under-abundance in heavy elements compared to the others – i.e. it was less massive so it formed fewer heavy elements and stars. This study is immensely significant when it comes to galactic formation and evolution, mainly because it is the first numerical simulation that has succeeded in reproducing a galaxy in such detail.
It is also of significance given that such a recent impact it could have left materials in the Local Group. In other words, this study could have implications that range far beyond our galactic neighborhood. It is also a good example of how increasingly sophisticated instruments are leading to more detailed observations which, when combined with increasingly sophisticated computers and algorithms, are leading to more detailed models.
One can only wonder if future extra-terrestrial intelligence (ETI) will draw similar conclusions about our own galaxy once it merges with Andromeda, billions of years from now. The collision and resulting features are sure to be of interest to anyone advanced species that’s around to study it!
Astrophotographer Rogelio Vernal Andreo with his gear all set up. His rig is a complex set up, including dual Takahashi telescopes photographing the same part of the sky simultaneously. Image; Rogelio Bernal Andreo (DeepSkyColors.com) (CC BY-NC-ND 3.0)
An astrophotographer in California has captured images of Elon Musk’s Tesla Roadster on its journey around our Sun. In the early morning of February 9th, Rogelio Bernal Andreo captured images of the Roadster as it appeared just above the horizon. To get the images, Andreo made use of an impressive arsenal of technological tools.
Andreo knew that photographing the Roadster would be a challenge, since it was over a million miles away at the time. But he has the experience and equipment to pull it off. The first task was to determine where the Tesla would be in the sky. Luckily, NASA’s JPL creates lists of coordinates for objects in the sky, called ephemerides. Andreo found the ephemeris for Starman and the Roadster, and it showed that the pair would be in the Hydra constellation, and that they would be only about 20 degrees above the horizon. That’s a challenge, because it means photographing through more atmospheric density.
The Tesla Roadster and its pilot “Starman” leaving Earth behind. Image: SpaceX
However, the Roadster and its driver would be bright enough to do it. As Andreo says in his blog, “The ephemeris from the JPL also indicated that the Roadster’s brightness would be at magnitude 17.5, and I knew that’s perfectly achievable.” So he gathered his gear, hopped in his vehicle, and went for it.
Andreo’s destination was the Monte Bello Open Space Preserve, a controlled-access area for which he has a night-time use permit. This area is kind of close to the San Francisco Bay Area, so the sky is a little bright for astrophotography, but since the Roadster has a magnitude of 17.5, he thought it was doable. Plus, it’s a short drive from his home.
Once he arrived there, he set up his impressive array of gear: dual telescopes and cameras, along with a tracking telescope and computers running specialized software. Andreo explains it best:
“Let me give you a brief description of my gear – also the one I use for most of my deep-sky images. I have a dual telescope system: two identical telescopes and cameras in parallel, shooting simultaneously at the very same area of the sky – same FOV, save a few pixels. The telescopes are Takahashi FSQ106EDX. Their aperture is 106mm (about 4″) and they give you a native 530mm focal length at f/5. The cameras are SBIG STL11k monochrome CCD cameras, one of the most legendary full-frame CCD cameras for astronomy (not the best one today, mind you, but still pretty decent). All this gear sits on a Takahashi EM-400 mount, the beast that will move it at hair-thin precision during the long exposures. I brought the temperature of the CCD sensors to -20C degrees (-4F) using the CCD’s internal cooling system.”
CCD’s with internal cooling systems. Very impressive!
The Takahashi FSQ106. Two of these beasts are at the heart of Andreo’s astrophotography system. Image: Takahashi Telescopes
Andreo uses a specialized focusing system to get his images. He uses focusers from Robofocus and precision focusing software called FocusMax. He also uses a third, smaller telescope called an autoguider. It focuses on a single star in the Field of View and follows it religiously. When that star moves, the whole rig moves. As Andreo says on his blog, “Autoguiding provides a much better mount movement than tracking, which is leaving up to the mount to blindly “follow” the sky. By actually “following” a star, we can make sure there’ll be no trails whether our exposures are 2 or 30 minutes long.”
Once he was all set up, there was time pressure. The Roadster would only be above the horizon for a short time and the Moon was coming up and threatening to wash out the sky. Andreo got going, but his first shots showed nothing.
Where the Roadster should be, Andreo’s photos showed nothing. But he wasn’t deterred. Image: Rogelio Bernal Andreo, (DeepSkyColor.com) (CC BY-NC-ND 3.0)
Andreo felt that once he got home and could process the images properly, the Tesla Roadster and its driver would be somewhere in his images. He kept taking pictures until about 5 AM. Cold and tired, he finally packed up his gear and went home.
“…no matter what I did, I could not find the Roadster.” Astrophotographer Rogelio Bernal Andreo
After some sleep, he began working with his images. “After a few hours of sleep, I started playing with the data and no matter what I did, I could not find the Roadster. I kept checking the coordinates, nothing made sense. So I decided to try again. The only difference would be that this time the Moon would rise around 3:30am, so I could try star imaging at 2:30am and get one hour of Moon-free skies, maybe that would help.”
Rogelio Bernal Andreo is a very accomplished astrophotographer. His images have been chosen as NASA’s Astronomy Photo of the Day over 50 times. This close-up of the Orion Nebula was chosen as APOD on June 4, 2017. The three bright stars are Orion’s belt. Image: Rogelio Bernal Andreo (DeepSkyColors.com) (CC BY-NC-ND 3.0)
So Andreo set out to capture the Roadster again. The next night, at the same location, he set up his gear again. But this time, some clouds rolled in, and Andreo got discouraged. He stayed to wait for the sky to improve, but it didn’t. By about 4 AM he packed up and headed home.
After a nap, he went over his photos, but still couldn’t find the Roadster. It was a puzzle, because he knew the Roadster’s coordinates. Andreo is no rookie, his photos have been published many times in Astronomy Magazine, Sky and Telescope, National Geographic, and other places. His work has also been chosen as NASA’s APOD (Astronomy Picture of the Day) more than 50 times. So when he can’t find something in his images that should be there, it’s puzzling.
Then he had an A-HA! moment:
“Then it hit me!! When I created the ephemeris from the JPL’s website, I did not enter my coordinates!! I went with the default, whatever that might be! Since the Roadster is still fairly close to us, parallax is significant, meaning, different locations on Earth will see Starman at slightly different coordinates. I quickly recalculate, get the new coordinates, go to my images and thanks to the wide field captured by my telescopes… boom!! There it was!! Impossible to miss!! It had been right there all along, I just never noticed!”
Andreo is clearly a dedicated astrophotographer, and this is a neat victory for him. He deserves a tip of the hat from space fans. Why not check out his website—his gallery is amazing!—and share a comment with him.
Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser
On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Originally mistaken for a comet, follow-up observations conducted by the European Southern Observatory (ESO) and others confirmed that ‘Oumuamua was actually a rocky body that had originated outside of our Solar System.
Since that time, multiple investigations have been conducted to determine ‘Oumuamua’s structure, composition, and just how common such visitors are. At the same time, a considerable amount of attention has been dedicated to determining the asteroid’s origins. According to a new study by a team of international researchers, this asteroid had a chaotic past that causes it to tumble around chaotically.
As they indicate, the discovery of ‘Oumuamua has provided scientists with the first opportunity to study a planetesimal born in another planetary system. In much the same way that research into Near-Earth Asteroids, Main Belt Asteroids, or Jupiter’s Trojans can teach astronomers about the history and evolution of our Solar System, the study of a ‘Oumuamua would provide hints as to what was going on when and where it formed.
For the sake of their study, Dr. Fraser and his international team of colleagues have been measuring ‘Oumuamua brightness since it was first discovered. What they found was that ‘Oumuamua wasn’t spinning periodically (like most small asteroids and planetesimals in our Solar System), but chaotically. What this means is that the asteroid has likely been tumbling through space for billions of years, an indication of a violent past.
While it is unclear why this is, Dr. Fraser and his colleagues suspect that it might be due to an impact. In other words, when ‘Oumuamua was thrown from its own system and into interstellar space, it is possible it collided violently with another rock. As Dr. Fraser explained in a Queen’s University Belfast press release:
“Our modelling of this body suggests the tumbling will last for many billions of years to hundreds of billions of years before internal stresses cause it to rotate normally again. While we don’t know the cause of the tumbling, we predict that it was most likely sent tumbling by an impact with another planetesimal in its system, before it was ejected into interstellar space.”
These latest findings mirror what other studies have been able to determine about ‘Oumuamua based on its object changes in its brightness. For example, brightness measurements conducted by the Institute for Astronomy in Hawaii – and using data from the ESO’s Very Large Telescope (VLT) – confirmed that the asteroid was indeed interstellar in origin, and that its shape is highly elongated (i.e. very long and thin).
However, measurements of its color have produced little up until now other than confusion. This was due to the fact that the color appeared to vary between measurements. When the long face of the object is facing telescopes on Earth, it appears largely red, while the rest of the body has appeared neutral in color (like dirty snow). Based on their analysis, Dr. Fraser and his team resolved this mystery by indicating that the surface is “spotty”.
In essence, most of the surface reflects neutrally, but one of its long faces has a large red region – indicating the presence of tholins on its long surface. A common feature of bodies in the outer Solar System, tholins are organic compounds (i.e. methane and ethane) that have turned a deep shade of reddish-brown thanks to their exposure to ultra-violet radiation.
What this indicates, according to Dr. Fraser, is broad compositional variations on ‘Oumuamua, which is unusual for such a small body:
“We now know that beyond its unusual elongated shape, this space cucumber had origins around another star, has had a violent past, and tumbles chaotically because of it. Our results are really helping to paint a more complete picture of this strange interstellar interloper. It is quite unusual compared to most asteroids and comets we see in our own solar system,” comments Dr Fraser.
Oumuamua as it appeared using the William Herschel Telescope on the night of October 29. Queen’s University Belfast/William Herschel Telescope
To break it down succinctly, ‘Oumuamua may have originated closer to its parent star (hence its rocky composition) and was booted out by strong resonances. In the course of leaving its system, it collided with another asteroid, which sent it tumbling towards interstellar space. It’s current chaotic spin and its unusual color are both testaments to this turbulent past, and indicate that its home system and the Solar System have a few things in common.
Since its arrival in our system, ‘Oumuamua has set off a flurry of scientific research. All over the world, astronomers are hoping to get a glimpse of it before it leaves our Solar System, and there are even those who hope to mount a robotic mission to rendezvous with it before its beyond our reach (Project Lyra). In any event, we can expect that this interstellar visitor will be the basis of scientific revelations for years to come!
This study is the third to be published by their team, which has been monitoring ‘Oumuamua since it was first observed in October. All studies were conducted with support provided by the Science and Technology Facilities Council.
On February 6th, 2018, SpaceX successfully launched its Falcon Heavy rocket into orbit. This was a momentous occasion for the private aerospace company and represented a major breakthrough for spaceflight. Not only is the Falcon Heavy the most powerful rocket currently in service, it is also the first heavy launch vehicle that relies on reusable boosters (two of which were successfully retrieved after the launch).
Equally interesting was the rocket’s cargo, which consisted of Musk’s cherry-red Tesla Roadster with a spacesuit in the driver’s seat. According to Musk, this vehicle and its “pilot” (Starman), will eventually achieve a Hohmann Transfer Orbit with Mars and remain there for up to a billion years. However, according to a new study, there’s a small chance that the Roadster will collide with Venus or Earth instead in a few eons.
Elon Musk’s Tesla Roadster being loaded aboard the Falcon Heavy’s payload capsule. Credit: SpaceX
As we indicated in a previous post, Musk’s original flight plan has the potential to place the Roadster into a stable orbit around Mars… after a fashion. According to Max Fagin, an aerospace engineer from Colorado and a space camp alumni, the Roadster will get close enough to Mars to establish an orbit by October of 2018. However, this orbit would not rule out close encounters with Earth over the course of the next few million years.
For the sake of their study, Rein and his colleagues considered how such close encounters might alter the Roadster’s orbit in that time. Using data from NASA’s HORIZONS interface to determine the initial positions of all Solar planets and the Roadster, the team calculated the likelihood of future close encounters between the vehicle and the terrestrial planets, and how likely a resulting collision would be.
As they indicated, the Roadster bears some similarities to Near-Earth Asteroids (NEAs) and ejecta from the Earth-Moon system. In short, NEAs permeate the inner Solar System, regularly crossing the orbits of terrestrial planets and experiencing close encounters with them (resulting in the occasional collision). In addition, ejecta from the Earth and Moon also experience close encounters with the terrestrial planets and collide with them.
However, the Tesla Roadster is unique in two key respects: For one, it originated from Earth rather than being pulled from the Asteroid Belt into the inner Solar System by strong resonances. Second, it had a higher ejection velocity when it left Earth, which tends to result in fewer impacts. “Given the peculiar initial conditions and even stranger object, it therefore remains an interesting question to probe its dynamics and eventual fate,” they claim.
The Falcon Heavy Rocket being fired up at launch site LC-39A at NASA’s Kennedy Space Center in Cape Canaveral, Florida. Credit: SpaceX
Another challenge was how the probability of an impact will change drastically over time. While the chance of a collision can be ruled out in the short run (i.e. the next few years), the Roadster’s chaotic orbit is difficult to predict over the course of subsequent close encounters. As such, the team performed a statistical calculation to see how the orbit and velocity of the Roadster would change over time. As they state in their study:
“Given that the Tesla was launched from Earth, the two objects have intersecting orbits and repeatedly undergo close encounters. The bodies reach the same orbital longitude on their synodic timescale of ~2.8 yrs.”
They began by considering how the Roadster’s orbit would evolve over the course of its next 48 orbits, which would encompass the next 1000 years. They then expanded the analysis to consider long-term evolution, which encompassed 240 orbits over the course of the next 3.5 million years. What they found was that on a million-year timescale, the orbit of the Roadster remains in a region dominated by close encounters with Earth.
However, over time, their simulations show that the Roadster will experience changes in eccentricity due to resonant and secular effects. This will result in interactions more frequent interactions between the Roadster and Venus over time, and close encounters with Mars becoming possible. Over long enough timescales, the team even anticipates that interactions with Mercury’s orbit will be possible (though unlikely).
Don’t Panic StarMan, Don’t Panic. Credit: SpaceX
In the end, their simulations revealed that over the course of a million years and beyond, the probability of a collision with a terrestrial planet is unlikely, but not impossible. And while the odds are slim, they favor an eventual collision with Earth. Or as they put it:
“Although there were several close encounters with Mars in our simulations, none of them resulted in a physical collision. We find that there is a ~6% chance that the Tesla will collide with Earth and a ~2.5% chance that it will collide with Venus within the next 1 Myr. The collision rate goes down slightly with time. After 3 Myr the probability of a collision with Earth is ~11%. We observed only one collision with the Sun within 3 Myr.”
Given the Musk hoped that his Roadster would remain in orbit of Mars for one billion years, and that aliens might eventually find it, the prospect of it colliding with Earth or Venus is a bit of a letdown. Why bother sending such a unique payload into space if it’s just going to come back? Still, the odds that it will be drifting through space for millions of years remains a distinct possibility.
And if there are any worries that the Roadster will pose a threat to future missions or Earth itself, consider the message Starman was looking at during his ascent into space – Don’t Panic! Assuming humanity is even alive eons from now, the far greater danger will be that such an antique will burn up in our atmosphere. After millions of years, Starman is sure to be a big celebrity!
The ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) instrument collects the light from all four of the 8.2-metre telescopes of the ESO's Very Large Telescope in Chile. The combined light-collecting area makes it the largest optical telescope in existence. Image: ESO/L. Calcada
It’s been 20 years since the first of the four Unit Telescopes that comprise the ESO’s Very Large Telescope (VLT) saw first light. Since the year 2000 all four of them have been in operation. One of the original goals of the VLT was to have all four of the ‘scopes work in combination, and that has now been achieved.
The instrument that combines the light from all four of the VLT ‘scopes is called ESPRESSO, which stands for Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations. ESPRESSO captures the light from each of the 8.2 meter mirrors in the four Unit Telescopes of the VLT. That combination makes ESPRESSO, in effect, the largest optical telescope in the world.
The huge diffraction grating is at the heart of the ultra-precise ESPRESSO spectrograph. In this image, the diffraction grating is undergoing testing in the cleanroom at ESO Headquarters in Garching bei München, Germany. Image: ESO/M. Zamani
Combining the power of the four Unit Telescopes of the VLT is a huge milestone for the ESO. As ESPRESSO instrument scientist at ESO, Gaspare Lo Curto, says, “ESO has realised a dream that dates back to the time when the VLT was conceived in the 1980s: bringing the light from all four Unit Telescopes on Cerro Paranal together at an incoherent focus to feed a single instrument!” The excitement is real, because along with its other science goals, ESPRESSO will be an extremely powerful planet-hunting telescope.
“ESO has realised a dream that dates back to the time when the VLT was conceived in the 1980s.” – Gaspare Lo Curto, ESPRESSO instrument scientist.
ESPRESSO uses a system of mirrors, lenses, and prisms to transmit the light from each of the four VLT ‘scopes to the spectrograph. This is accomplished with a network of tunnels that was incorporated into the VLT when it was built. ESPRESSO has the flexibility to combine the light from all four, or from any one of the telescopes. This observational flexibility was also an original design goal for ESPRESSO.
The four Unit Telescopes often operate together as the VLT Interferometer, but that’s much different than ESPRESSO. The VLT Interferometer allows astronomers to study extreme detail in bright objects, but it doesn’t combine the light from the four Unit Telescopes into one instrument. ESPRESSO collects the light from all four ‘scopes and splits it into its component colors. This allows detailed analysis of the composition of distant objects.
ESPRESSO team members gather in the control room during ESPRESSO’s first light. Image: ESO/D. Megevand
ESPRESSO is a very complex instrument, which explains why it’s taken until now to be implemented. It works with a principle called “incoherent focus.” In this sense, “incoherent” means that the light from all four telescopes is added together, but the phase information isn’t included as it is with the VLT Interferometer. What this boils down to is that while both the VLT Interferometer and ESPRESSO both use the light of all four VLT telescopes, ESPRESSO only has the spatial resolution of a single 8.2 mirror. ESPRESSO, as its name implies, is all about detailed spectrographic analysis. And in that, it will excel.
“ESPRESSO working with all four Unit Telescopes gives us an enticing foretaste of what the next generation of telescopes, such as ESO’s Extremely Large Telescope, will offer in a few years.” – ESO’s Director General, Xavier Barcons
ESPRESSO is the successor to HARPS, the High Accuracy Radial velocity Planet Searcher, which up until now has been our best exoplanet hunter. HARPS is a 3.6 meter telescope operated by the ESO, and also based on an echelle spectrograph. But the power of ESPRESSO will dwarf that of HARPS.
There are three main science goals for ESPRESSO:
Planet Hunting
Measuring the Variation of the Fundamental Physical Constants
Analyzing the Chemical Composition of Stars in Nearby Galaxies
Planet Hunting
ESPRESSO will take highly precise measurements of the radial velocities of solar type stars in other solar systems. As an exoplanet orbits its star, it takes part in a dance or tug-of-war with the star, the same way planets in our Solar System do with our Sun. ESPRESSO will be able to measure very small “dances”, which means it will be able to detect very small planets. Right now, our planet-hunting instruments aren’t as sensitive as ESPRESSO, which means our exoplanet search results are biased to larger planets. ESPRESSO should detect more smaller, Earth-size planets.
The four Unit Telescopes that make up the ESO’s Very Large Telescope, at the Paranal Observatory> Image: By ESO/H.H.Heyer [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons
Measuring the Variation of the Fundamental Physical Constants
This is where the light-combining power of ESPRESSO will be most useful. ESPRESSO will be used to observe extremely distant and faint quasars, to try and measure the variation of the fundamental physical constants in our Universe. (If there are any variations, that is.) It’s not only the instrument’s light-combining capability that allows this, but also the instrument’s extreme stability.
Specifically, the ESPRESSO will try to take our most accurate measurements yet of the fine structure constant, and the proton to electron mass ratio. Astronomers want to know if these have changed over time. They will use ESPRESSO to examine the ancient light from these distant quasars to measure any change.
Analyzing the Chemical Composition of Stars in Nearby Galaxies
ESPRESSO will open up new possibilities in the measurement of stars in nearby galaxies. It’s high efficiency and high resolution will allow astronomers to study stars outside of the Milky Way in unprecedented detail. A better understanding of stars in other galaxies is always a priority item in astronomy.
We’ll let Project Scientist Paolo Molaro have the last word, for now. “This impressive milestone is the culmination of work by a large team of scientists and engineers over many years. It is wonderful to see ESPRESSO working with all four Unit Telescopes and I look forward to the exciting science results to come.”
Special Guests:
Joe Pappalardo is the author of the new popular science and technology book, Spaceport Earth: The Reinvention of Spaceflight (The Overlook Press; Available Now). In it, Pappalardo “tackles the ever-changing, 21st-century space industry and what privately funded projects like Elon Musk’s SpaceX mean for the future of space travel.” (Foreign Policy)
Spaceport Earth takes readers on a tour of these high-stakes sites as Pappalardo examines how private companies are reshaping the way we use, intend to use, and view space travel, not solely for scientific exploration but for increasingly more general travel. Visiting every working spaceport in the United States and rocket launches around the world, Pappalardo presents a travelogue and modern history of spaceflight — where the industry is now and what’s on the horizon for explorers and consumers alike—in Spaceport Earth.
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Chris Prophet, author of SpaceX From the Ground Up, joins us again to discuss with Fraser last week’s Falcon Heavy success.
Announcements:
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