Posted on by Matt Williams

Hubble Takes Advantage Of Opposition To Snap Jupiter

Image of Jupiter, taken by the Hubble Space Telescope when the planet was at a distance of 670 million kilometers from Earth. Credit: NASA/ESA/A. Simon (GSFC)

On April, 7th, 2017, Jupiter will come into opposition with Earth. This means that Earth and Jupiter will be at points in their orbit where the Sun, Earth and Jupiter will all line up. Not only will this mean that Jupiter will be making its closest approach to Earth – reaching a distance of about 670 million km (416 million mi) – but the hemisphere that faces towards us will be fully illuminated by the Sun.

Because of its proximity and its position, Jupiter will be brighter in the night sky than at any other time during the year. Little wonder then why NASA and the ESA are taking advantage of this favorable alignment to capture images of the planet with the Hubble Space Telescope. Already, on April 3rd, Hubble took the wonderful color image (shown above) of Jupiter, which has now been released.

Using its Wide Field Camera 3 (WFC3), Hubble was able to observe Jupiter in the visible, ultraviolet and infrared spectrum. From these observations, members of the Hubble science team produced a final composite image that allowed features in its atmosphere – some as small as 130 km across – to be discernible. These included Jupiter’s colorful bands, as well as its massive anticyclonic storms.

Image of Jupiter’s Great Red Spot, taken by the Voyager 1 space probe during its flyby on March 5, 1979, and re-processed on November 6, 1998. Credit: NASA/JPL

The largest of these – the Great Red Spot – is believed to have been raging on the surface ever since it was first observed in the 1600s. In addition, it is estimated that the wind speeds can reach up to 120 m/s (430 km/h; 267 mph) at its outer edges. And given its dimensions – between 24-40,000 km from west to east and 12-14,000 km from south to north – it is large enough to swallow the Earth whole.

Astronomers have noticed how the storm appears to have been shrinking and expanding throughout its recorded history. And as the latest images taken by Hubble (and by ground-based telescopes) have confirmed, the storm continues to shrink. Back in 2012, it was even suggested that the Giant Red Spot might eventually disappear, and this latest evidence seems to confirm that.

No one is entirely sure why the storm is slowly collapsing; but thanks to images like these, researchers are gaining a better understanding of what mechanisms power Jupiter’s atmosphere. Aside from the Great Red Spot, the similar but smaller anticyclonic storm in the farther southern latitudes – aka. Oval BA or “Red Spot Junior” – was also captured in this latest image.

Located in the region known as the South Temperate Belt, this storm was first noticed in 2000 after three small white storms collided. Since then, the storm has increased in size, intensity and changed color (becoming red like its “big brother”). It is currently estimated that wind speeds have reached 618 km/h (384 mph), and that it has become as large as Earth itself (over 12,000 km, 7450 mi in diameter).

Image of Jupiter, made during the Outer Planet Atmospheres Legacy (OPAL) programme on January 19th, 2015. Credit: NASA/ESA/A. Simon (GSFC)/M. Wong (UC Berkeley)/G. Orton (JPL-Caltech)

And then there are the color bands that make up Jupiter’s surface and give it its distinct appearance. These bands are essentially different types of clouds that run parallel to the equator and differ in color based on their chemical compositions. Whereas the whiter bands have higher concentrations of ammonia crystals, the darker (red, orange and yellow) have lower concentrations.

Similarly, these color patterns are also affected by the upwelling of compounds that change color when they are exposed to ultraviolet light from the Sun. Known as chromophores, these colorful compounds are likely made up of sulfur, phosphorous and hydrocarbons. The planet’s intense wind speeds of up to 650 km/h (~400 mph) also ensure that the bands are kept separate.

These and other observations of Jupiter are part of the Outer Planet Atmospheres Legacy (OPAL) progamme. Dedicated to ensuring that Hubble gets as much information as it can before it is retired – sometime in the 2030s or 2040s – this program ensures that time is dedicated each year to observing Jupiter and the other gas giants. From the images obtained, OPAL hopes to create maps that planetary scientists can study long after Hubble is decommissioned.

The project will ultimately observe all of the giant planets in the Solar System in a wide range of filters. The research that this enables will not only help scientists to study the atmospheres of the giant planets, but also to gain a better understanding of Earth’s atmosphere and those of extrasolar planets. The programme began in 2014 with the study of Uranus and has been studying Jupiter and Neptune since 2015. In 2018, it will begin viewing Saturn.

Further Reading: Hubble Space Telescope

Posted on by Matt Williams

Finally! A Low Mass Super-Earth With Some Funky Atmosphere

Artist's impression of the exoplanet GJ 1132 b, which orbits the red dwarf star GJ 1132. Astronomers have managed to detect the atmosphere of this Earth-like planet. Credit: MPIA

In 2015, astronomers discovered an intriguing extrasolar planet located in a star system some 39 light years from Earth. Despite orbiting very close to its parent star, this “Venus-like” planet – known as GJ 1138b – appeared to still be cool enough to have an atmosphere. In short order, a debate ensued as to what kind of atmosphere it might have, whether it was a “dry Venus” or a “wet Venus”.

And now, thanks to the efforts of an international team of researchers, the existence of an atmosphere has been confirmed around GJ 1138b. In addition to settling the debate about the nature of this planet, it also marks the first time that an atmosphere has been detected around a low-mass Super-Earth. On top of that, GJ 1138b is now the farthest Earth-like planet that is known to have an atmosphere.

Led by John Southworth (of Keele University) and Luigi Mancini (of the University of Rome Tor Vergata), the research team included members from the Max Planck Institute for Astronomy (MPIA), the National Institute for Astrophysics (INAF), the University of Cambridge and Stockholm University. Their study, titled “Detection of the atmosphere of the 1.6 Earth mass exoplanet GJ 1132b“, recently appeared in The Astrophysical Journal.

Artist’s impression of the “Venus-like” exoplanet GJ 1132b. Credit: cfa.harvard.edu

Using the GROND imager on the La Silla Observatory’s 2.2m ESO/MPG telescope, the team monitored GJ 1132b in different wavelengths as it transited in front of its parent star. Given the planet’s orbital period (1.6 days), these transits happen quite often, which presented plenty of opportunities to view it pass in front of its star. In so doing, they monitored the star for slight decreases in its brightness.

As Dr. Southworth explained to Universe via email, these observations confirmed the existence of an atmosphere:

“What we did was to measure the amount of dimming at 7 different wavelengths in optical and near-infrared light. At one of these wavelengths (IR) the planet seemed to be slightly bigger. This indicated that the planet has a large atmosphere around it which allows most of the starlight to pass through, but is opaque at one wavelength.”

The team members from the University of Cambridge and the MPIA then conducted simulations to see what this atmosphere’s composition could be. Ultimately, they concluded that it most likely has a thick atmosphere that is rich in water and/or methane – which contradicted recent theories that the planet had a thin and tenuous atmosphere (i.e. a “dry Venus”).

The ESO’s Paranal Observatory, located in the Atacama Desert of Chile. Credit: ESO

It was also the first time that an atmosphere has been confirmed around a planet that is not significantly greater in size and mass to Earth. In the past, astronomers have detected atmospheres around many other exoplanets. But in these cases, the planets were either gas giants or planets that were many times Earth’s size and mass (aka. “Super-Earths”). GJ 1132b, however, is 1.6 times as massive as Earth, and measures 1.4 Earth radii.

In addition, these findings are a significant step in the search for life beyond our Solar System. At present, astronomers seek to determine the chemical composition of a planet’s atmosphere to determine if it could be habitable. Where the right combination of chemical imbalances exist, the presence of living organisms is seen as a possible cause.

By being able to determine that a planet at lower end of the super-Earth scale has an atmosphere, we are one step closer to being able to determine exoplanet habitability. The detection of an atmosphere-bearing planet around an M-type (red dwarf) star is also good news in and of itself. Low-mass red dwarf stars are the most common star in the galaxy, and recent findings have indicated that they might be our best shot for finding habitable worlds.

Besides detecting several terrestrial planets around red dwarf stars in recent years – including seven around a single star (TRAPPIST-1) – there is also research that suggests that these stars are capable of hosting large numbers of planets. At the same time, there have been concerns about whether red dwarfs are too variable and unstable to support habitable worlds.

Artist’s impression of Kepler-1649b, the “Venus-like” world orbiting an M-class star 219 light-years from Earth. Credit: Danielle Futselaar

As Southworth explained, spotting an atmosphere around a planet that closely orbits a red dwarf could help bolster the case for red dwarf habitability:

“One of the big issues has been that very-low-mass stars typically have strong magnetic fields and thus throw out a lot of X-ray and ultraviolet light. These high-energy photons tend to destroy molecules in atmospheres, and might also evaporate them completely. The fact that we have detected an atmosphere around GJ 1132b means that this kind of planet is indeed capable of retaining an atmosphere for billions of years, even whilst being bombarded by the high-energy photons from their host stars.

In the future, GJ 1132b is expected to be a high-priority target for study with the Hubble Space Telescope, the Very Large Telescope (VLT) at the Paranal Observatory in Chile, and next-generation telescopes like the James Webb Space Telescope (scheduled for launch in 2018). Already, observations are being made, and the results are being eagerly anticipated.

I’m sure I’m not the only one who would like to hear what astronomers discover as they set their sights on this nearby star system and it’s Venus-like world! In the meantime, be sure to check out this video about GJ 1132b, courtesy of MIT news:

Further Reading: Max Planck Institute for Astronomy

Posted on by Matt Williams

When Will Mars Be Close to Earth?

Approximately every two years, Earth and Mars are at the closest point to each other in their orbits (i.e. opposition). Credit: NASA

As neighboring planets, Earth and Mars have a few things in common. Both are terrestrial in nature (i.e. rocky), both have tilted axes, and both orbit the Sun within its circumstellar habitable zone. And during the course of their orbital periods (i.e. a year), both planets experience variations in temperature and changes in their seasonal weather patterns.

However, owing to their different orbital periods, a year on Mars is significantly longer than a year on Earth – almost twice as long, in fact. And because their orbits are different, the distance between our two planets varies considerably. Basically, every two years Earth and Mars will go from being “at conjunction” (where they are farther from each other) to being “at opposition” (where they are closer to each other).

Orbital Period:

Earth orbits the Sun at an average distance (semi-major axis) of 149,598,023 km (92,955,902 mi; or 1 AU), ranging from 147,095,000 km (91,401,000 mi) at perihelion to 152,100,000 km (94,500,000 mi) at aphelion. At this distance, and with an orbital velocity of 29.78 km/s (18.5 mi/s) the time it take for the planet to complete a single orbit of the Sun (i.e. orbital period) is equal to about 365.25 days.

A top-down image of the orbits of Earth and Mars. Credit: NASA

Mars, meanwhile, orbits the Sun at an average distance of 227,939,200 km (141,634,850 mi; or 1.523679 AU), ranging from 206,700,000 km (128,437,425 mi) at perihelion to 249,200,000 km (154,845,700 mi) at aphelion. Given this difference in distance, Mars orbits the Sun at a slower speed (24.077 km/s; 14.96 mi/s) and takes about 687 Earth days (or 668.59 Mars sols) to complete a single orbit.

In other words, a Martian year is almost 700 days long, which works out to being 1.88 times as long as a year on Earth. This means that every time Mars completes a single orbit around the Sun, the Earth has gone around almost twice. During the moments when they are on opposite sides of the Sun, this is known as a “conjunction”. When they are on the same side of the Sun, they are at “opposition”.

Mars Opposition:

By definition, a “Mars opposition” occurs when planet Earth passes in between the Sun and planet Mars. The term refers to the fact that Mars and the Sun appear on opposite sides of the sky. Because of their orbits, Mars oppositions happens about every 2 years and 2 months – 779.94 Earth days to be precise. From our perspective here on Earth, Mars appears to be rising in the east just as the Sun sets in the west.

About every two years, the Earth passes Mars as they orbit around the Sun. Credit: NASA

After staying up in the sky for the entire night, Mars then sets in the west just as the Sun begins to rise in the east.  During an opposition, Mars becomes one of the brightest objects in the night sky, and is easy to see with the naked eye. Through small telescopes, it will appear as a large and bright object. Through larger telescopes, Mars’ surface features will even become apparent, which would include its polar ice caps.

An opposition can also occur anywhere along Mars’ orbit. However, opposition does not necessary mean that the two planets are at their closest overall. In truth, it just means that they are are at their closest point to each other within their current orbital period. If Earth and Mars’ orbits were perfectly circular, they would be closest to each other whenever they were at opposition.

Instead, their orbits are elliptical, and Mars’ orbit is more elliptical than Earth’s – which means the difference between their respective perihelion and aphelion is greater. Gravitational tugging from other planets constantly changes the shape of our orbits too – with Jupiter pulling on Mars and Venus and Mercury affecting Earth.

Color composite of Mars from seven of its previous oppositions, taken with the Hubble Space Telescope. Credit: NASA/ESA/HST

Lastly, Earth and Mars do not orbit the Sun on the exact same plane – i.e. their orbits are slightly tilted relative to each other. Because of this, Mars and Earth become closest to each other only over the long-term. For instance, every 15 or 17 years, an opposition will occur within a few weeks of Mars’ perihelion. When it happens while the Mars is closest to the sun (called “perihelic opposition”), Mars and Earth get particularly close.

And yet, the closest approaches between the two planets only take place over the course of centuries, and some are always closer than others. To make matters even more confusing, over the past few centuries, Mars’ orbit has been getting more and more elongated, carrying the planet even nearer to the Sun at perihelion and even farther away at aphelion. So future perihelic oppositions will bring Earth and Mars even closer.

On August 28th, 2003, astronomers estimated that Earth and Mars were just 55,758,118 km (34,646,488 mi; 0.37272 AU) apart. This was the closest the two planets had come to each other in almost 60,000 years. This record will stand until August 28th, 2287, at which point the planets will be an estimated 55,688,405 km (34,603,170.6 mi; 0.372254 AU) from each other.

Future Oppositions:

Want to organize your schedule for the next time Mars will be close to Earth? Here are some upcoming dates, covering the next few decades. Plan accordingly!

  • July 27th, 2018
  • October 13th, 2020
  • December 8th, 2022
  • January 16th, 2025
  • February 19th, 2027
  • Mar 25th, 2029
  • May 4th, 2031
  • June 27th, 2033
  • September 15th, 2035
  • November 19th, 2037
  • January 2nd, 2040
  • February 6th, 2042
  • March 11th, 2044
  • April 17th, 2046
  • June 3rd, 2048
  • August 14th, 2050

And in case your interested, Mars will be making close approaches on two occasions this century. The first will take place on August 14th, 2050, when Mars and Earth will be 55.957 million km (34.77 million mi; or 0.374051 AU) apart; and on September 1st, 2082, when they will be 55,883,780 km (34,724,571 mi; 0.373564 AU) apart.

There’s a reason missions to Mars depart from Earth every two years. Seeking to take advantage of shorter travel times, rovers, orbiters and landers are launched to coincide with Mars being at opposition. And when it comes time to send crewed mission to Mars (or even settlers) the same timing will apply!

We have written many interesting articles about Mars here at Universe Today. Here’s How Far is Mars from Earth?, How Long Does it Take to Get to Mars?, How Long is a Year on Mars?, How Far is Mars from the Sun?, and How Long Does it Take Mars to Orbit the Sun?

For more information, here’s a comprehensive schedule of upcoming Mars oppositions.

Astronomy Cast also has some wonderful episodes on the Red Planet. Here’s Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:

Posted on by Nancy Atkinson

Confirmed: Ceres Has a Transient Atmosphere

This image of Ceres approximates how the dwarf planet's colors would appear to the eye. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Sometimes they see it, sometimes they don’t. That’s why scientists have never been completely sure if Ceres has an atmosphere or not. But now data from the Dawn spacecraft — in orbit of Ceres — confirms the dwarf planet really does have a very weak atmosphere, but it comes and goes.

The on-again-off-again nature of Ceres’ atmosphere appears to be linked to solar activity. When energetic particles from the Sun hit exposed ice within the craters on Ceres, the ice can sublimate and create an “exosphere” that lasts for a week or so.

Michaela Villarreal from UCLA, lead author of the new study, and her team wrote in their paper that the “atmosphere appeared shortly after the passage of a large enhancement in the local flux of high-energy solar protons,” and explained that when energetic particles from the Sun hit exposed ice and ice near the surface of the dwarf planet, it transfers energy to the water molecules as they collide. This frees the water molecules from the ground, allowing them to escape and create a tenuous atmosphere.

NASA’s Dawn spacecraft determined the hydrogen content of the upper yard, or meter, of Ceres’ surface. Blue indicates where hydrogen content is higher, near the poles, while red indicates lower content at lower latitudes. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

A process like this could also be taking place on the Moon, and is likely similar to the process similar to what takes place on comets.

“Our results also have implications for other airless, water-rich bodies of the solar system, including the polar regions of the moon and some asteroids,” said Chris Russell, principal investigator of the Dawn mission, also at UCLA. “Atmospheric releases might be expected from their surfaces, too, when solar activity erupts.”

There have been hints of an atmosphere at Ceres since the early 1990’s. In 1991, the International Ultraviolet Explorer satellite detected hydroxyl emission from Ceres, but not in 1990. Then, in 2007, the European Southern Observatory’s Very Large Telescope searched for a hydroxide emission, but came up empty. The European Space Agency’s Herschel Space Observatory detected water vapor as a possible weak atmosphere, on three occasions, but did not on a fourth attempt.

Dwarf planet Ceres is located in the asteroid belt, between the orbits of Mars and Jupiter. Observations by ESA’s Herschel space observatory between 2011 and 2013 find that the dwarf planet has a thin water-vapour atmosphere. It is the first unambiguous detection of water vapour around an object in the asteroid belt. The inset shows the water absorption signal detected by Herschel on 11 October 2012. Copyright ESA/ATG medialab/Küppers et al.

The Dawn spacecraft itself saw evidence of a transient atmosphere when it arrived at Ceres in March 2015, with data from its Gamma Ray and Neutron Detector instrument. It also has found ample evidence for water in the form of ice, found just underground at higher latitudes, where temperatures are lower. Ice has been detected directly at the small bright crater called Oxo and in at least one of the craters that are persistently in shadow in the northern hemisphere. Other research has suggested that persistently shadowed craters are likely to harbor ice. Additionally, the shapes of craters and other features are consistent with significant water-ice content in the crust.

The team’s research shows the atmosphere doesn’t necessarily show up when Ceres is close to the Sun or when sunlight hits the ice directly, but from energetic particles released by the Sun when its activity level is high. For example, the best detections of Ceres’ atmosphere did not occur at its closest approach to the Sun.

Also, the times where no atmosphere was detected coincided with lower solar activity, so the researchers say this suggests that solar activity, rather than Ceres’ proximity to the Sun, is a more important factor in generating an exosphere.

Ceres actually is now getting closer to the Sun. However, since the Sun appears to be in a very quiet period, Villarreal, Russell and team predict an atmosphere won’t show up, that the dwarf planet will have little to no atmosphere for some time. However, they said both Dawn and other observatories should keep an eye on what’s happening at Ceres.

Paper: The Dependence of the Cerean Exosphere on Solar Energetic Particle Events

JPL press release

Posted on by Matt Williams

What Are You Doing For Yuri’s Night?

What are you doing for Yuri's Night? Credit: yurisnight.net

On April 12th, 1961, history was made when the first human being – Russian cosmonaut Yuri Gagarin – went into space. Similarly, on April 12th, 1981, the inaugural launch of the Space Shuttle took place. In recognition of these accomplishments, people from all around the world have been celebrating “Yuri’s Night” – a global festival honoring humanity’s past, present, and future in space – for over a decade and a half.

This year will mark the 56th anniversary of Yuri Gagarin’s historic flight and of human spaceflight in general. As with every Yuri’s Night that has happened since 2001, this year’s festivities will feature educational events, presentations and games (along with general revelry) at venues located all across the world. Do you have any plans for Yuri’s Night 2017? And if not, perhaps you would like to know what’s happening?

Plenty of events have been planned for this year that are sure to appeal to science enthusiasts and those with a passion for space exploration. One of the highlights for 2017 is a chance to enjoy a virtual reality space vacation, which comes courtesy of the fun folks at Guerilla Science – a London and New York-based group that specializing in creating educational events and installations for festivals, museums, galleries, etc.

Screen shot from Guerilla Science’s “space vacation” VR app. Click to see the animation. Credit: guerillascience.org

For the sake of this year’s Yuri’s night, they are offering people a chance to experience a VR application that allows people to experience a trip to Mars’ Mariner Valley, or to take a self-guided tour on the Moon using the clicker to navigate. To learn more about this application (which is also available for beta testing), be sure to check out Guerilla Science’s “Intergalactic Travel Bureau“. As they describe the bureau’s purpose on their website:

“The Intergalactic Travel Bureau is a live, interactive experience that explores the incredible possibilities of space tourism through personalized space vacation planning experiences. It’s a little bit like Virgin Galactic and SpaceX meet the Jetsons and Mad Men. Bringing together space scientists, astronomers, science educators, actors and the general public, the Bureau has popped up all over the UK and the US since 2011.”

In addition, a virtual event is being hosted by Spacelog, a volunteer organization dedicated to sharing mission transcripts and photographs that celebrate the history of space exploration. In commemoration of Gagarin’s historic flight, they will be publishing the transcripts of the Vostok 1 mission on their Facebook page. Like the mission itself, the event will start at 4:10 am UTC and conclude at 07:55 UTC on Wednesday, April 12th.

For those interested, the Yuri’s Night Global Team (led by Veronica Ann Zabala-Aliberto) is still seeking Regional Team Leaders to help provide support, coordination, and resources for the hundreds of Yuri’s Night parties that have been planned. In addition to organizers and outreach personnel, the Global Team is also seeking translators who are fluent in Arabic and Turkish. To check out what positions are available, go to their website.

Statue of Yuri Gagarin, the first man in space, at the Baikonur Cosmodrome. Credit: AFP

So far, a total of 127 events have been registered in 38 countries, and on 7 continents. That’s right, an event has even been planned for Antarctica, specifically in Loung B3 at the South Pole Station (located at the geographic South Pole). So if you’re in the area – for whatever reason, possibly doing field studies on Emperor Penguins or something! – be sure to swing by!

To find an event in your neck of the woods, consult the full list here. And if you are interested in hosting one, you can register at the Yuri’s Night website. The website is also looking for donations to keep their volunteer and community efforts going.

Wherever you happen to land on April 12th, be sure to raise a glass to all those who have risked life and limb over the past fifty-plus years to establish humanity as a space-faring species!

Further Reading: Yuri’s Night

Posted on by Matt Williams

A Star Going Supernova In Slow Motion Discovered

Artistic impression of a star going supernova, casting its chemically enriched contents into the universe. Credit: NASA/Swift/Skyworks Digital/Dana Berry

A supernova is a rare and wondrous event. Since these intense explosions only take place when a massive star reaches the final stage of its evolutionary lifespan – when it has exhausted all of its fuel and undergoes core collapse – or when a white dwarf in a binary star system consumes its companion, being able to witness one is quite the privilege.

But recently, an international team of astronomers witnessed something that may be even rarer – a supernova event that appeared to be happening in slow-motion. Whereas supernova of its kind (SN Type Ibn) are typically characterized by a rapid rise to peak brightness and a fast decline, this particular supernova took an unprecedentedly long time to reach maximum brightness, and then slowly faded away.

For the sake of their study, the research team – which included members from the UK, Poland, Sweden, Northern Ireland, the Netherlands and Germany – studied a Type Ibn event known as OGLE-2014-SN-13. These types of  explosions are thought to be the result of massive stars (which have lost their outer envelop of hydrogen) undergoing core-collapse, and whose ejecta interacts with a cloud of helium-rich circumstellar material (CSM).

OGLE-2014-SN-131 (blue circle) in a VLT acquisition (left), and an NTT image showing no visible host at the SN location (right). Credit: Karamehmetoglu et al.

The study was led by Emir Karamehmetoglu of The Oskar Klein Center at Stockholm University. As he told Universe Today via email:

“Type Ibn supernovae are thought to be the explosions of very massive stars, surrounded by a dense region of extremely helium-rich material. We infer the existence of this Helium via the presence of narrow helium emission lines in their optical spectra. We also believe that there is very little, if any Hydrogen in the immediate surrounding of the star, because if it was there, it would show up much stronger than the Helium in the spectra. As you can imagine, this sort of configuration is very rare, since hydrogen is the most abundant element in the universe by far.”

As already noted, Type Ibn supernova are characterized by a sudden and dramatic increase in their brightness, then a rapid decline. However, when observing OGLE-2014-SN-131 – which they detected on November 11th, 2014 using the Optical Gravitational Lensing Experiment (OGLE) at the Warsaw University Astronomical Observatory – they witnessed something completely different.

“OGLE-2014-SN-131 was different because it took almost 50 days, as compared to the more typical ~1 week, for it to become bright,” said Karamehmetoglu. “Then it declined relatively slowly as well. The fact that it took several times longer than the typical rise to maximum brightness, which is unlike any other Ibn that has been studied before, makes it a very unique object.”

The Optical Gravitational Lensing Experiment (OGLE), a project being undertaken by the Astronomical Observatory at the University of Warsaw. Credit: astrouw.edu.pl

Thanks to data obtained by the OGLE-IV Transient Detection System, they were able to place OGLE-2014-SN-131 at a distance of about 372 ± 9 megaparsecs (1183.95  to 1242.66 million light years) from Earth. This was then followed-up with photometric observations using the OGLE telescope at the Las Campanas Observatory in Chile and the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) at the La Silla Observatory.

The team also obtained spectroscopic data using the ESO’s New Technology Telescope (NTT) at La Silla and the Very Large Telescope (VLT) at the Paranal Observatory (both located in Chile). In addition to having an unusually long rise-time, the combined data also indicated that the supernova had an unusually broad light curve. To explain all this, the team considered a number of possibilities.

For starters, they considered standard radio-active decay models, which are known to power the lightcurves of most other Type I and Type II supernovae. However, these could not account for what they had observed with OGLE-2014-SN-131. As such, they began considering more exotic scenarios, which included energy being input from a young, rapidly spinning neutron star (aka. a magnetar) nearby.

While this model would explain the behavior of OGLE-2014-SN-131, it was limited in that it is not yet known what circumstances would be needed to invoke a magnetar. As such, Karamehmetoglu and his team also considered the possibility that the explosions might be powered by shocks created by the interaction of ejected material from the supernova with the helium-rich CSM.

Supernova 2008D in galaxy NGC 2770 (Type Ib), shown in X-ray (left) and visible light (right). Credit: NASA/Swift Science Team/Stefan Immler

Thanks to the spectral data obtained by the NTT and VLT, they knew that such material existed around the star, and the model was therefore able to reproduce the observed behavior. As Karamehmetoglu explained, it is for this reason that they favor this model over the others:

“In this scenario, the reason OGLE-2014-SN-131 is different from other Type Ibn SNe is due to the unusually massive nature of its progenitor star. A very massive star, between 40-60 times the mass of our Sun, located in a low-metallicity galaxy, probably gave rise to this SN by expelling a great amount of helium-rich matter, then eventually exploding as a SN.”

In addition to being a unique event, this study also some drastic implications for astronomy and the study of supernovae. Thanks to the detection of OGLE-2014-SN-131, any future models that attempt to explain how Type Ibn supernovae form now have a stringent constraint. At the same time, astronomers now have an existing model to consider if and when they witness other supernovae which exhibit particularly long rise times.

Looking ahead, this is precisely what Karamehmetoglu and his colleagues hope to do. “In our next effort, we will study other, less-rare, types of SN that have long rise times, and therefore are probably created by very massive stars,” he said. “We will get to take advantage of the comparison frame-work we developed when studying OGLE-2014-SN-131.”

Once more, the Universe has taught us that two of the more important aspects of scientific research are adaptability and a commitment to continuous discovery. When things don’t conform to existing models, develop new ones and test them out!

Further Reading: arXiv

Posted on by David Dickinson

By Jove: Jupiter at Opposition 2017

Jupiter from January 7th, 0217. Image credit and copyright: Fred Locklear.
Jupiter from January 7th, 0217. Image credit and copyright: Fred Locklear.

Been missing the evening planets? Currently, Saturn and Venus rule the dawn, and Mars is sinking into the dusk as it recedes towards the far side of the Sun. The situation has been changing for one planet however, as Jupiter reaches opposition this week.

Jupiter in 2017

Currently in the constellation Virgo near the September equinoctial point where the celestial equator meets the ecliptic in 2017, Jupiter rules the evening skies. Orbiting the Sun once every 11.9 years, Jupiter moves roughly one zodiacal constellation eastward per year, as oppositions for Jupiter occur about once every 399 days.

As the name implies, “opposition” is simply the point at which a planet seems to rise “opposite” to the setting Sun.

At opposition 2017 on Friday, April 7th, Jupiter shines at magnitude -2.5 and is 666.5 million kilometers distant. Jupiter just passed aphelion on February 16th, 2017 at 5.46 AU 846 million kilometers from the Sun, making this and recent oppositions slightly less favorable. An April opposition for Jupiter also means it’ll now start to occur in the southern hemisphere for this and the next several years. Jupiter crosses the celestial equator northward again in 2022.

The path of Jupiter through 2017. Image credit: Starry Night.

Can you see Ganymede with the naked eye? Shining at magnitude +4.6, the moon lies just on the edge of naked eye visibility from a dark sky site… the problem is, the moon never strays more than 5′ from the dazzling limb of Jupiter. Here’s a fun and easy experiment: attempt to spot Ganymede through this month’s opposition season, using nothing more than a pair of MK-1 eyeballs. Then at the end of the month, check an ephemeris for greatest elongations of the moon. Any matches?

With binoculars, the first thing you’ll notice is the four bright Galilean moons of Io, Europa, Ganymede and Callisto. At about 10x magnification or so, Jupiter will begin to resolve as a disk. With binoculars, you get a very similar view of Jupiter as Galileo had with his primitive spy glass.

At the telescope eyepiece at low power you can see the main cloud bands of Jove, the northern and southern equatorial belts. Shadow transits and eclipses of the Jovian moons are also fun to watch, and frequent for the innermost two moons Io and Europa.  Orbiting Jupiter once every seven days, transits of Ganymede are less frequent, and outermost Callisto is the only moon that can “miss” Jupiter on occasion, as it does this year until transits resume in 2020.

Jupiter an the Great Red Spot from January 29th, 2017. Image credit and copyright: Efrain Morales.

Jupiter’s one of the best planets for imaging: unlike Venus or bashful Mars, things are actually happening on the cloudtops of Jove. You can see smaller storms come and go as the Great Red Spot make its circuit once every 10 hours. Follow Jupiter from sunset through sunrise, and it will rotate just about all the way around once. Strange to think, we’ve been using modified webcams to image Jupiter for over a decade and a half now.

Jupiter and Io from 2006. Photo by author.

The major moons of Jupiter cast shadows nearly straight back as seen from our vantage point near opposition. After opposition, the shadows of the moons and the planet itself begin to slide to one side and will continue to do so as the planet heads towards quadrature 90 degrees east of the Sun. In 2017, quadrature for Jupiter occurs on July 5th as the planet sits due south for northern hemisphere observers at sunset. Distances to Jupiter vary through opposition, quadrature and solar conjunction, and Danish astronomer Ole Rømer used discrepancies in predictions versus actual observed phenomena of Jupiter’s moons to make the first good estimation of the speed of light in 1676.

Double shadow transits are also interesting to watch, and a season of double events involving Io and Europa begins next month on May 12th.

Jupiter will rule the dusk skies until solar conjunction on October 26th, 2017.

It’s also interesting to note that while the Northern Equatorial Belt has been permanent over the last few centuries of telescopic observation, the Southern Equatorial Belt seems to pull a disappearing act roughly every decade or so. This last occurred in 2010, and we might just be due again over the next few years. The Great Red Spot has also looked a little more pale and salmon over the last few years, and may vanish altogether this century.

Finally, the Full Moon typically sits near a given planet near opposition, as occurs next week on the evening of April 10/11th.

Jupiter, the Moon and Spica on the evening of April 10th. Credit: Stellarium.

The next occultation of Jupiter by the Moon occurs on October 31st, 2019.

Don’t miss a chance to observe the king of the planets in 2017.

– Here’s a handy JoveMoons for Android and Iphone for planning your next Jovian observing session.

-Be sure to check out our complete guide to oppositions, elongations, occultations and more with our 101 Astronomical Events for 2017, a free e-book from Universe Today.

-Send those images of Jupiter in to Universe Today’s Flickr forum.

Posted on by Matt Williams

World’s Largest Rocket Will Be Recoverable & Reusable

The Falcon Heavy, once operational, will be the most powerful rocket in the world. Credit: SpaceX

When Elon Musk launched SpaceX in 2002, he did so with the intention of making reusability a central feature of his company. Designed to lower the costs associated with launches, being able to reuse boosters was also a means of making space more accessible. “If one can figure out how to effectively reuse rockets just like airplanes,” he said, “the cost of access to space will be reduced by as much as a factor of a hundred.”

And with last week’s successful launch of the first reusable Falcon 9 (the SES-10 Mission) Musk chose to unveil more details about his company’s next major milestone. According to Musk, the demonstration flight of the Falcon Heavy – which is scheduled to take place this summer – will involve two recovered Falcon 9 cores and the attempted recovery of the rocket’s upper-stage.

In other words, on its maiden flight, two of the three boosters sending the Falcon Heavy into orbit will be reused, and SpaceX may even try to attempt to make the first-ever recovery of a second stage. Such a feat, if successful, will signal that Musk’s dream of total reusability – where the first stage, payload fairings, and second stage of their launch vehicles are all recoverable – has come to fruition.

An artist's illustration of the Falcon Heavy rocket. Image: SpaceX
An artist’s illustration of the Falcon Heavy rocket. Image: SpaceX

According to details shared at the news conference that accompanied the launch of SES-10, Musk indicated that the test flight would make use of boosters that were recovered from two successful Falcon 9 launches, and that all three would be recovered after launch. As he was quoted as saying by Stephen Clark at SpaceFlightNow:

“That will be exciting mission, one way or another. Hopefully in a good direction. The two side boosters will come back and do sort of a synchronized aerial ballet and land. Two of the side boosters will land back at the Cape. That’ll be pretty exciting to see two come in simultaneously, and the center core will land downrange on the drone ship.”

On the following day – Friday, March. 31st, 11:44 am – Musk followed this up with a tweet that indicated that the test flight could also involve something that has never before been attempted. “”Considering trying to bring upper stage back on Falcon Heavy demo flight for full reusability,” he wrote. “Odds of success low, but maybe worth a shot.”

Such a plan is in keeping with what Musk had initially hoped for his company, which was to make all of its rockets entirely reusable. While reusable boosters were not a part of the initial designs for the Falcon Heavy, the numerous successful recoveries (on land and at sea) of the first stage of the Falcon 9 indicated that the Heavy‘s outer cores could be recovered and reused in the same way.

Chart comparing the lift capacity of major launch systems to Low Earth Orbit (LEO). Credit: SpaceX

Musk also reiterated that the demo flight would be taking place this summer, and that it would be carrying something comically-inspired. “Silliest thing we can imagine!” he tweeted, in response to a question of what the cargo would be. “Secret payload of 1st Dragon flight was a giant wheel of cheese. Inspired by a friend & Monty Python.”

For those unfamiliar with what Musk was referring to “The Cheese Shop”, a classic Monty Python sketch. From this, we can safely assume that Musk has something similar in mind for the inaugural Falcon Heavy launch. Perhaps some wine and bread to go with that cheese?

The demonstration flight – which will take place on launch pad 39A at the Kennedy Space Center in Florida – is already expected to be a momentous event. With the ability to lift payloads of over 64 metric tons (64,000 kg or 141,096 lbs) to Low Earth Orbit (LEO), the Falcon Heavy will be the most powerful rocket currently in operation.

In fact, its capacity will be about twice that of the Arianespace Ariane 5 and United Launch Alliance’s Delta IV Heavy rockets – which are capable of lifting 21,000 kg (46,000 lb) and 28,790 kg (63,470 lb) to LEO, respectively. However, SpaceX has indicated that the payload performance to geosynchronous transfer orbit (GTO) would be reduced with the addition of reusable technology.

Artist’s concept of the SpaceX Red Dragon spacecraft launching to Mars on SpaceX Falcon Heavy as soon as 2018. Credit: SpaceX

Whereas its original capacity to GTO was said to be 22,200kg (48,940 lb), full reusability on all three booster cores will reduce this to 7,000 kg (15,000 lb), while having two reusable outside cores will reduce it to approximately 14,000 kg (31,000 lb). But of course, these reductions in payloads have to be considered against significantly reduced launch costs.

For the time being, the plan is to recover all three boosters of the Falcon Heavy. This may change, depending on the success of the maiden flight, to the point where just the outer boosters are deemed reusable and the central core expendable. And depending on the success of the second stage recovery, SpaceX may begin pursuing reusability with the second stages of their Falcon 9 as well.

Musk has also indicated that at present, SpaceX will be primarily focused on the many commercial missions it has planned using the Falcon 9 launch vehicle. But if all goes according to plan, this summer will be the second time in the space of a single year that Musk’s and the aerospace company he started knocked it out of the park and silenced all those who said he was attempting the impossible.

Further Reading: SpaceFlightNow, SpaceX

Posted on by Ken Kremer

Worlds’ 1st Recycled Booster from SpaceX Sails Serenely at Sunrise into Port Canaveral – Photo/Video Gallery

World’s first reflown rocket booster - the SpaceX Falcon 9 first stage - sails back into Port Canaveral, FL just before sunrise atop OCISLY droneship on which it landed 9 minutes after March 30, 2017 liftoff from KSC with SES-10 telecomsat - as seen entering channels mouth trailing a flock of birds from Jetty Park pier on April 4, 2017. Credit: Ken Kremer/Kenkremer.com
World’s first reflown rocket booster – the SpaceX Falcon 9 first stage – sails back into Port Canaveral, FL just before sunrise atop OCISLY droneship on which it landed 9 minutes after March 30, 2017 liftoff from KSC with SES-10 telecomsat – as seen entering channels mouth trailing a flock of birds from Jetty Park pier on April 4, 2017. Credit: Ken Kremer/Kenkremer.com

PORT CANAVERAL/KENNEDY SPACE CENTER, FL – Basking in the sunrise glow, the world’s first recycled booster – namely a SpaceX Falcon 9 – sailed serenely into Port Canaveral this morning, Tuesday, April 4, atop the tiny droneship on which it soft landed shortly after launching on March 30 for an unprecedented second time.

Shortly before sunrise, SpaceX’s recovered Falcon 9 first stage triumphantly arrived on Tuesday at the mouth of Port Canaveral and the public pier at Jetty Park around 7 am – greeted by excited onlookers, media and space buffs eager to be an eyewitness to the first rocket to launch and land two times fully intact !

The Falcon 9 standing proudly erect on the football field sized OCISLY droneship landing pad was towed into port by the Elsbeth III in the wee morning hours around 7 am. The ships made their way majestically along the channel westwards until reaching the docking port.

World’s first reflown rocket booster – the SpaceX Falcon 9 first stage – sails back into Port Canaveral, FL just before sunrise atop OCISLY droneship on which it landed 9 minutes after March 30, 2017 liftoff from KSC with SES-10 telecomsat – as seen being towed into channels mouth from Jetty Park pier on April 4, 2017. Credit: Ken Kremer/Kenkremer.com

Check out this expanding gallery of eyepopping photos and videos from several space journalist colleagues and friends and myself – for views you won’t see elsewhere.

Click back as the arrival gallery grows !

Twice flown Falcon 9 first stage arrives into Port Canaveral on April 4, 2017 floating atop droneship. Credit: Julian Leek

The milestone SpaceX mission to refly the first ever ‘used rocket’ blasted off right on time at the opening of the dinnertime launch window on Thursday, March 30, at 6:27 p.m. EDT.

The used two stage 229-foot-tall (70-meter) rocket carried the SES-10 telecommunications payload to orbit using a ‘Flight-Proven’ Falcon 9 rocket from seaside Launch Complex 39A at NASA’s Kennedy Space Center (KSC) in Florida.

1st recycled SpaceX Falcon 9 booster is hoisted off OCISLY droneship after arriving and docking at Port Canaveral, FL on April 4, 2017. Credit: Ken Kremer/Kenkremer.com

After the 156 foot tall first stage booster completed its primary mission task, SpaceX engineers successfully guided it to a second landing on the tiny Of Course I Still Love You – OCISLY – drone ship for a soft touchdown some eight and a half minutes after liftoff.

“This is a huge revolution in spaceflight,” billionaire SpaceX CEO and Chief Designer Elon Musk told reporters at the post launch briefing at the Kennedy Space Center press site, barely an hour after liftoff.

Musk’s goal is to drastically reduce the cost of spaceflight so that it will one day lead to a ‘City on Mars’.

Recovered and twice flown and landed SpaceX Falcon 9 first stage stands chained to the deck of the OCISLY droneship as seen being towed into the mouth of Port Canaveral channels from Jetty Park pier on April 4, 2017. It launched on March 30, 2017 from KSC and delivered SES-10 telecomsat to GTO. Credit: Ken Kremer/Kenkremer.com

OCISLY had left Port Canaveral several days ahead of the March 30 launch and was prepositioned in the Atlantic Ocean some 400 miles (600 km) off the US East coast, just waiting for the boosters 2nd history making approach and pinpoint propulsive soft landing.

This recycled Falcon 9 first stage booster had initially launched a year ago in April 2016 for NASA on the SpaceX Dragon CRS-8 resupply mission to the International Space Station (ISS) under contract for the space agency.

Check out these exquisite videos showing various aspects of the Port arrival and processing:

Video Caption: This video shows the return of the first re-used SpaceX Falcon 9 booster to Port Canaveral on 4/4/17 in detail. After launching the SES-10 satellite on 3/30/17 it then landed on the OCISLY drone ship for the second time. The video highlights OCISLY’s return to port and docking. The booster was then hoisted off the droneship with a crane and stationed on a pedestal on land for processing. Credit: Jeff Seibert

Video Caption: The booster looks ready for another flight after arriving in to Port Canaveral, FL on 4 April 2017 and launching/landing from KSC on 30 March 2017. Elon Musk has said it will be put on display in Florida. This is a total game changer for the rocket industry. Credit:USLaunchReport

After making its way picturesquely through Port Canaveral channel, the droneship was docked, Workers soon attached a metal cap to the top of the first stage.

Next they removed the restraining chains fastening the booster to the deck. Next they hoisted it off the droneship with a work crane and transported it onto a work pedestal on the ground for further processing.

By late evening I observed that the workers were still busily operating on the booster. They were welding the metal cap to the top of the booster. All 4 landing legs were still attached as of 10 p.m. EDT on Tuesday, April 4.

The legs will soon be detached so the booster can be rotated horizontal and trucked back to the huge hangar at pad 39A.

Watch for Ken’s continuing coverage direct from onsite at the Kennedy Space Center press site and Cape Canaveral Air Force Station.

Workers weld cap to top of relaunched/recovered SpaceX Falcon 9 at night with gorgeous water reflections after hoisting it off the OCISLY droneship onto ground work platform at Port Canaveral, FL on April 4, 2017 . Credit: Ken Kremer/Kenkremer.com

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Workers process the relaunched/recovered SpaceX Falcon 9 at night with gorgeous water reflections after hoisting it off the OCISLY droneship onto ground work platform at Port Canaveral, FL on April 4, 2017 . Credit: Ken Kremer/Kenkremer.com
SpaceX CEO and Chief Designer Elon Musk and SES CTO Martin Halliwell exuberantly shake hands of congratulation following the successful delivery of SES-10 TV comsat to orbit using the first reflown and flight proven booster in world history at the March 30, 2017 post launch media briefing at NASA’s Kennedy Space Center in Florida. Credit: Ken Kremer/Kenkremer.com
Closeup of base of reflown SpaceX Falcon 9 first stage rocket and 4 landing legs after Port Canaveral arrival on droneship on Apr 4, 2017. Credit: Julian Leek
ELSBETH III towing OCISLY and Falcon 9, next to Jetty Park pier at the entrance to Port Canaveral channel. Good fisherman story… “hey I think I just caught me a big rocket!” As reflown SpaceX Falcon 9 floats by on OCISLY droneship onlookers and fisherman watch from Jetty Park pier on 4 April 2017. Credit: Chuck Higgins

Slowly making their way down Port Canaveral channel as the Sun continues to rise on ELSBETH III towing OCISLY. Credit: Carol Higgins
Reflown SpaceX Falcon 9 on OCISLY is towed by ELSBETH III and slowly makes its way down Port Canaveral channel as the Sun continues to rise and buzzards keep watch. Credit: Jean Wright

1st reflown/relanded SpaceX Falcon 9 booster sails past pelicans and pleasure craft atop OCISLY droneship through Port Canaveral channel, FL on April 4, 2017. Credit: Ken Kremer/Kenkremer.com
Posted on by Nancy Atkinson

Cassini’s Final Mission to Annihilation Starts April 22

This illustration shows Cassini above Saturn's northern hemisphere prior to one of its 22 Grand Finale dives. Credit: NASA/JPL-Caltech

Grab the tissues. This video nearly had the Cassini team all choked up during today’s press briefing, and virtual sobs and sniffs were abundant on social media posts sharing the video.

“We get goosebumps and get emotional every time we see it,” said Earl Maize, Cassini project manager at JPL.

On April 22 the Cassini spacecraft will begin its ‘Grand Finale’ — the beginning of the end of this tremendous mission that has provided breathtaking images and so many new discoveries of Saturn, its rings and moons. The mission will end on September 15, 2017, when it makes a dramatic plunge into the gas giant.

Here’s the video that had everyone teary-eyed. Be prepared for some stunning visuals:

Today, Maize talked about how nineteen countries and three space agencies contributed to the success of the Cassini/Huygens mission, saying the mission has been truly an international triumph and a phenomenal achievement.

“Cassini’s legacy is assured. We are in the books!” Maize said. “But the best is yet to come. We are going to dive into the gap between the rings of Saturn and Saturn’s atmosphere, a place where no spacecraft has ever gone. We’ll be going 70,000 mph (112,634 km/hr) into a 1,500-mile-wide (2,400-kilometer) gap, operating the spacecraft from a billion miles away.”

Cassini has been a relatively trouble free mission, and has made many discoveries about the Saturn system. So why crash the spacecraft?

Cassini is running out of fuel, basically running on fumes at this point.* And NASA needs to follow the protocol of planetary protection, and not allow a spacecraft with possible microbes from Earth to crash into a potentially habitable moon such as Enceladus or Titan.

“Cassini’s own discoveries were its demise,” Maize said. “Enceladus has a warm, salt water ocean. We can’t risk an inadvertent contact with this pristine body. The only choice was to destroy it (Cassini) in a designed fashion.”

Maize said that back in 2010, the team decided they would make the mission last as long as possible and use every last kilogram of propellant to explore the Saturn system as thoroughly as they could.

Cassini vs. Saturn. As depicted in this illustration, Cassini will plunge into Saturn’s atmosphere on Sept. 15, 2017. Using its attitude control thrusters, the spacecraft will work to keep its antenna pointed at Earth while it sends its final data, including the composition of Saturn’s upper atmosphere. Credit: NASA/JPL-Caltech

The final flyby of Titan on April 22 will ultimately alter Cassini’s trajectory and push it toward the spacecraft’s final demise. Maize described the gravity slingshot from Titan as a “last kiss goodbye that will push Cassini into Saturn. This is a roller coaster ride that we’re not coming out of.”

You can plot Cassini’s trajectory in JPL’s “Eyes on Cassini” special section of their Eyes on the Solar System website.

Cassini will make 22 passes through the gap, and in doing so, further our understanding of how giant planets, and planetary systems everywhere, form and evolve.

Project Scientist Linda Spilker said Cassini will be able to make close up measurements of Saturn and its rings to finally help us understand the mass and internal structure of Saturn. And the images should be absolutely stunning.

There’s the risk of dust or debris hitting the spacecraft, potentially crippling Cassini. But the risk is worth it, because if the spacecraft survives through even just a few of the close passes, the scientific payback will be incredible. However, even if the spacecraft is crippled and can’t send back its final science observations, the end is inevitable, as the path toward destruction will be written by the final ‘kiss’ from Titan.

“This is something we couldn’t try at any other time,” Maize said. “But now is time.”

A computer-generated representation of all Cassini’s Saturn orbits -affectionately called the “ball of yarn” by mission planners. The time frame spans Saturn Orbit Insertion on July 1, 2004 to the end of mission on Sept. 15, 2017. Credit: NASA/JPL-Caltech.

The Cassini team said the end of the mission will likely be a combination of excitement, pride and a sense of loss.

“I think that once the signal is lost, it would mean the heartbeat of Cassini is gone,” said Spilker. “I think there will be tremendous cheers and applause for the completion of an absolutely incredible mission. Hugs, tears — the Kleenex box will be passed around — but we will rejoice at being part of such a wonderful mission.”

See more images and information about the Grand Finale here.

For more of an inside look at Cassini, I devote a chapter of my book to the mission, with more insight from Earl Maize, Linda Spilker and others about the history and discoveries of the Cassini/Huygens mission, and additional details about the Grand Finale. “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Channging Our View of the Cosmos.”

Artist’s concept of Cassini orbiter crossing Saturn’s ring plane.
Credit: NASA/Jet Propulsion Laboratory.

*One of the Cassini team members said that as of today (April 4, 2017) Cassini has 36kg of hydrazine left for the thrusters, which are used everyday to orient the spacecraft, point the antenna towards Earth, point the instruments to their desired targer, etc. For the Titan flyby on April 22, about 10-15 kg. As for the bipropellant that runs the main engines, that’s a little more unknown and the one the team is worried most about running out of fuel. The team member said there is about 10 kg of that fuel left, “plus or minus 20 kilos [meaning there is true uncertainty about how much of this fuel remains]. We could run out today, or we could have 30 kilos left.”