Saturn from June 1st. Image credit and copyright: Peter on the Universe Today Flickr forum.
Saturn on June 1st, nearing opposition. Image credit and copyright: Peter on the Universe Today Flickr forum
Summertime astronomy leaves observers with the perennial question: when to observe? Here in Florida, for example, true astronomical darkness does not occur until 10 PM; folks further north face an even more dire situation. In Alaska, the game in late July became “on what date can you first spot a bright planet/star? around midnight.
And evening summer thunder showers don’t help. Our solution is to get up early (4 AM or so) when the roiling atmosphere has settled down a bit.
But there’s one reason to stay up late, as the planet Saturn reaches opposition next week on June 15th and crosses into the evening sky.
Southern hemisphere observers have it best this year, as the ringed planet loiters in southern declinations for the next few years. In fact, Saturn won’t pop up over the celestial equator again until April, 2026. You’ll still be able to see Saturn from mid-northern latitudes, looking low to the south.
First, a brief rundown of the planets this summer. Mars is currently on the far side of the Sun and headed towards solar conjunction of July 26th. Meanwhile, Mercury is headed towards greatest eastern (dusk) elongation on June 21st. Early AM viewers, can follow Venus, which has just passed greatest elongation west of the Sun on June 3rd, just last week. Finally, Jupiter joins Saturn in the dusk sky, high to the south at sunset and headed towards quadrature 90 degrees east of the Sun on July 6th.
Looking eastward on the evening of June 9th. Credit: Stellarium.
There’s another astronomical curiosity afoot this coming weekend: the MiniMoon for 2017. This is the Full Moon nearest to lunar apogee, a sort of antithesis of the over-hyped “SuperMoon.” Lunar apogee occurs on Thursday, June 8th and the Full Moon occurs just 14 hours after.
2017 sees Saturn traveling from the dreaded “13th constellation” of zodiac Ophiuchus the Serpent Bearer into Sagittarius. This also means that Saturn is headed towards bottoming out near 23 degrees southern declination next year in late 2018. Saturn truly lives up to its “father time” namesake, marking up its slow 29 year passage once around the zodiac. This struck home to us a few years back when Saturn passed Spica in the constellation Virgo, right back where I first started observing the planet as a teenager three decades before.
The path of Saturn through the last half of 2017. Credit: Starry Night Education Software.
The rings are also at their widest tilt in 2017, making for an extra photogenic view. 27 degrees wide as seen from our Earthly vantage point is as wide as Saturn’s ring system ever gets. Saturn isn’t really “tipping” back and forth as much as it’s orbiting the Sun and dipping one hemisphere towards us, and then another. In 2017, it’s the planet’s northern hemisphere time to shine.
Saturn: the changing view. Image credit and copyright: Andrew Symes (@failedprotostar)
Here’s the last/next cycle rundown:
-Rings wide open: (southern pole of Saturn tipped earthward): 2003
–Rings wide open: (northern pole of Saturn tipped earthward): 2017
-Rings edge on: 2025
-Rings wide open: (southern pole of Saturn tipped earthward): 2032
Even a small 60 mm refractor and a low power eyepiece will reveal the most glorious facet of Saturn: its glorious rings. Galileo first saw this confounding view in 1610, and sketched Saturn as a curious double-handled world. In 1655 Christaan Huygens first correctly deduced that Saturn’s rings are a flat plane, fully disconnected from the planet itself.
Crank up the magnification a bit, and the large Cassini Gap in the rings and the shadow play of the rings and the planet becomes apparent. This gives the view an amazing 3-D effect unparalleled in observational astronomy. The shadow cast by the bulk of the planet disappears behind it during opposition, then slowly starts to reemerge to one side after. Other things to watch for include the retro-reflector Seeliger Effect ( also known as opposition surge) as the planet brightens near opposition. And can you spy the bulk of the planet through the Cassini gap?
The moons of Saturn. Image credit and copyright: John Chumack
Hunting for Saturn’s moons is also a fun challenge. Saturn has more moons visible to a backyard telescope than any other planet. Titan is easiest, as the +8 magnitude moon orbits Saturn once every 16 days. In a small to medium-sized (8-inch) telescope, six moons are readily visible: Enceladus, Mimas, Rhea, Dione, Iapetus and Tethys. Large light bucket scopes 10” and larger might just also tease out the two faint +15th magnitude moons Hyperion and Phoebe.
Cassini looks back across Saturn’s rings. NASA/Cassini/JPL-Caltech/Space Science Institute
There’s also something else special about Saturn in 2017 in the world of space flight: the venerable Cassini mission comes to an end this September. Hard to believe, this mission soon won’t be with us. Launched in 1997, Cassini arrived at Saturn in in July 2004, and has since provided us with an amazing decade plus of science. The internet and science writing online has grown up with Cassini, and it’ll be a sad moment to see it go.
All thoughts to ponder, as you check out Saturn at the eyepiece this summer.
Meanwhile the already berthed Orbital ATK Cygnus OA-7 supply ship departed the station on Sunday, June 4 after ground controllers detached it and maneuvered it into position for departure.
The commercial Dragon cargo freighter carrying nearly 3 tons of science and supplies for the multinational crew on the CRS-11 resupply mission reached the space stations vicinity Monday morning, June 5, after a two day orbital chase starting from the Kennedy Space Center and a flawless series of carefully choreographed thruster firings culminated in rendezvous.
Liftoff of the SpaceX Falcon 9 rocket carrying the unmanned Dragon cargo freighter from seaside Launch Complex 39A at KSC in Florida took place during an instantaneous launch window at 5:07 p.m. EDT Saturday, June 3, following a 48 hour delay due to a stormy weather scrub at the Florida Space Coast on Thursday, June 1.
The stunning Falcon 9 launch and landing events were captured by journalists and tourists gathered from around the globe to witness history in the making with their own eyeballs.
The Falcon 9 blastoff also counts as the 100th flight from KSC’s historic pad 39A which previously launched NASA’s Apollo astronauts on lunar landing missions and space shuttles for 3 decades
Check out the 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 gallery grows !
1st Reused SpaceX Dragon cargo craft lifts off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. June 3, 2017 on CRS-11 mission carrying 3 tons of research equipment, cargo and supplies to the International Space Station. Credit: Ken Kremer/kenkremer.com
By 8:30 a.m. Monday morning ground controllers had maneuvered Dragon to within 250 meters of the station and the imaginary keep out sphere around the orbiting complex.
Engineers carefully assessed the health of the Dragon and its systems to insure its ability to slowly and safely move in closer for capture by the crew.
When Dragon reached a distance of 11 meters, it was grappled by Expedition 52 astronauts Peggy Whitson and Jack Fischer using the 57.7 foot long (17.6 meter long) Canadian-built robotic arm Monday morning at 9:52 a.m. EDT, a few minutes ahead of schedule.
“Capture complete,” radioed Whitson as Dragon was captured at its grapple pin by the grappling snares at the terminus of the Canadarm2 robotic arm.
Dragon’s capture took place as the ISS was orbiting 250 miles over the South Atlantic Ocean as it was nearing the East coast of Argentina.
“Complete complete. Go for capture configuration,” replied Houston Mission control.
The newly arrived SpaceX Dragon CRS-11 resupply ship is installed to the Harmony module on June 5, 2017. The Progress 66 cargo craft is docked to the Pirs docking compartment and the Soyuz MS-04 crew vehicle is docked to the Poisk module. Credit: NASA
“We want to thank the entire team on the ground that made this possible, both in Hawthorne and in Houston. Really around the whole world, from support in Canada for this wonderful robotic arm, Kennedy Space Center’s launch support, to countless organizations which prepared the experiments and cargo,” Fischer radioed in response.
“These people have supplied us with a vast amount of science and supplies, really fuel for the engine of innovation we get to call home, the International Space Station. We have a new generation of vehicles now, led by commercial partners like SpaceX, as they build the infrastructure that will carry us into the future of exploration.”
“It’s also the first second mission to the ISS which was previously here as CRS-4. The last returned visitor was space shuttle Atlantis on the STS-135 mission,” Fischer said.
A little over two hours after it was captured by Expedition 52 Flight Engineers Jack Fischer and Peggy Whitson, ground teams maneuvered the unpiloted SpaceX Dragon cargo craft for attachment to the Earth-facing port of the station’s Harmony module.
“Ground controllers at Mission Control, Houston reported that Dragon was bolted into place at 12:07 p.m. EDT as the station flew 258 statute miles over central Kazakhstan,” NASA reported.
The berthing of Dragon to Harmony was not broadcast live on NASA TV.
1st Reused SpaceX Dragon cargo craft lifts off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. June 3, 2017 on CRS-11 mission carrying 3 tons of research equipment, cargo and supplies to the International Space Station. Credit: Ken Kremer/kenkremer.com
Dragon CRS-11 marks SpaceX’s eleventh contracted commercial resupply services (CRS) mission to the International Space Station for NASA since 2012.
Check out these exquisite videos from a wide variety of vantage points including remote cameras at the pad and Cape Canaveral media viewing site – including an A/V compilation of sonic booms from the propulsive ground landing.
Video Caption: CRS-11 Launch from KSC Pad 39A with the first re-used Dragon capsule. SpaceX Falcon 9 launch of the CRS-11 mission to take supplies, equipment and experiments to the ISS, followed by the first stage landing at LZ-1 on the Cape Canaveral Air Force Station. Credit: Jeff Seibert
Video Caption: SpaceX Falcon 9/Dragon CRS 11 Launch 3 June 2017. Launch of SpaceX Falcon 9 on June 3, 2017 from pad 39A at the Kennedy Space Center, FL carrying 1st recycled Dragon supply ship bound for the International Space Station on the CRS-11 mission loaded with 3 tons of science and supplies – as seen in this remote video taken at the pad under cloudy afternoon skies. Credit: Ken Kremer/kenkremer.com
Video Caption: Sonic booms from the return of the CRS-11 booster to LZ-1 on June 3, 2017. Triple sonic booms signal the return of the Falcon 9 first stage to LZ-1 after launching the CRS-11 Dragon spacecraft to the ISS. Credit: Jeff Seibert
The gumdrop shaped 20-foot high, 12-foot-diameter Dragon is carrying almost 5,970 pounds of science experiments and research instruments, crew supplies, food water, clothing, hardware, gear and spare parts to the million pound orbiting laboratory complex.
SpaceX Falcon 9 booster deploys quartet of landing legs moments before precision propulsive ground touchdown at Landing Zone 1 on Canaveral Air Force Station barely nine minutes after liftoff from Launch Complex 39A on 3 June 2017 from the Kennedy Space Center in Florida on the Dragon CRS-11 resupply mission to the International Space Station for NASA. Credit: Ken Kremer/Kenkremer.com
The CRS-11 cargo ship will support over 62 of the 250 active research investigations and experiments being conducted by Expedition 52 and 53 crew members.
The flight delivered investigations and facilities that study neutron stars, osteoporosis, solar panels, tools for Earth-observation, and more.
40 new micestonauts are also aboard inside the rodent research habitat for a first of its kind osteoporosis science study – that seeks to stem the loss of bone density afflicting millions of people on Earth and astronauts crews in space by testing an experimental drug called NELL-1. The therapy will also examine whether bone can be regenerated for the first time. No drug exists for bone regeneration.
The unpressurized trunk of the Dragon spacecraft also transported 3 payloads for science and technology experiments and demonstrations.
The truck payloads include the Roll-Out Solar Array (ROSA) solar panels, the Multiple User System for Earth Sensing (MUSES) facility which hosts Earth-viewing instruments and tools for Earth-observation and equipment to study neutron stars with the Neutron Star Interior Composition Explorer (NICER) payload.
NICER is the first ever space mission to study the rapidly spinning neutron stars – the densest objects in the universe. The launch coincidentally comes nearly 50 years after they were discovered by British astrophysicist Jocelyn Bell.
A second objective of NICER involves the first space test attempting to use pulsars as navigation beacons through technology called Station Explorer for X-Ray Timing and Navigation (SEXTANT).
Blastoff of 1st recycled SpaceX Falcon 9 rocket from Launch Complex 39A at the Kennedy Space Center on June 3, 2017 delivering Dragon CRS-11 resupply mission to the International Space Station (ISS) for NASA. Credit: Ken Kremer/kenkremer.com
NASA decided to use the SpaceX weather related launch delay to move up the departure of the “SS John Glenn” Cygnus cargo ship by over a month since it was already fully loaded and had completed its mission to deliver approximately 7,600 pounds of supplies and science experiments to the orbiting laboratory and its Expedition 51 and 52 crew members for Orbital ATK’s seventh NASA-contracted commercial resupply mission called OA-7.
Named after legendary Mercury and shuttle astronaut John Glenn – 1st American to orbit the Earth – the supply ship had spent 44 days at the station.
The “SS John Glenn” will now remain in orbit a week to conduct the third SAFFIRE fire experiment as well as deploy four small Nanoracks satellites before Orbital ATK flight controllers send commands June 11 to deorbit the spacecraft for its destructive reentry into the Earth’s atmosphere over the Pacific Ocean.
The Orbital ATK Cygnus cargo craft, with its prominent Ultra Flex solar arrays, is pictured moments after being released from the International Space Station on June 4, 2017 . Credit: NASA TV
Watch for Ken’s onsite CRS-11 mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
SpaceX Falcon 9 aloft carrying 1st reused Dragon on CRS-11 resupply flight to the International Space Station on June 3, 2017 from Launch Complex 39A at the Kennedy Space Center. Credit: Ken Kremer/kenkremer.com Blastoff of SpaceX Falcon 9 with reused Dragon CRS-11 cargo craft from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. on June 3, 2017. Credit: Julian LeekDescent of SpaceX Falcon 9 1st stage towards Landing Zone-1 at Cape Canaveral after Jun 3, 2017 launch from pad 39A at the Kennedy Space Center. Credit: Julian LeekRecycled SpaceX Dragon CRS-11 cargo craft lifted off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. June 3, 2017 carrying 3 tons of research equipment, cargo and supplies to Earth orbit and the International Space Station. Credit: Ken Kremer/kenkremer.com3 June 2017 launch of SpaceX Falcon 9 on CRS-11 mission to the ISS – as seen from Port Orange, FL. Credit: Gerald DaBoseLanding of SpaceX Falcon 9 1st stage following launch of Dragon CRS-11 cargo craft from Launch Complex 39A at NASA’s Kennedy Space Center in Florida on June 3, 2017 to the ISS. Credit: Jean WrightSpaceX Falcon 9 rocket goes erect to launch position atop Launch Complex 39A at the Kennedy Space Center on 1 Jun 2017 as seen the morning before later afternoon launch from inside from the pad perimeter. Liftoff of the CRS-11 resupply mission to the International Space Station (ISS) slated for 1 June 2017. Credit: Ken Kremer/Kenkremer.comUp close view of SpaceX Dragon CRS-11 resupply vessel atop Falcon 9 rocket and delivering 3 tons of science and supplies to the International Space Station (ISS) for NASA. Liftoff slated for 1 June 2017. Credit: Ken Kremer/Kenkremer.com
Scientists may now know why the Boomerang Nebula, the coldest object in the known Universe. Credit: NASA/ESA/The Hubble Heritage Team (STScI/AURA)
The Boomerang Nebula, a proto-planetary nebula that was created by a dying red giant star (located about 5000 light years from Earth), has been a compelling mystery for astronomers since 1995. It was at this time, thanks to a team using the now-decommissioned 15-meter Swedish-ESO Submillimetre Telescope (SESTI) in Chile, that this nebula came to be known as the coldest object in the known Universe.
And now, over 20 years later, we may know why. According to a team of astronomers who used the Atacama Large Millimeter/submillimeter Array (ALMA) – located in the Atacama desert in northern Chile – the answer may involve a small companion star plunging into the red giant. This process could have ejected most of the larger star’s matter, creating an ultra-cold outflow of gas and dust in the process.
Composite image of the Boomerang Nebula, with ALMA observations (orange) showing the e hourglass-shaped outflow on top of an image from the Hubble Space Telescope (blue). Credit: ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble; NRAO/AUI/NSF
Originally discovered in 1980 by a team of astronomers using the Anglo-Australian telescope at the Siding Spring Observatory, the mystery of this nebula became apparent when astronomers noted that it appeared to be absorbing the light of the Cosmic Microwave Background (CMB). This background radiation, which is the energy leftover from the Big Bang, provides the natural background temperature of space – 2.725 K (–270.4 °C; -454.7 °F).
For the Boomerang Nebula to absorb that radiation, it had to be even colder than the CMB. Subsequent observations revealed that this was in fact the case, as the nebula has a temperature of less than half a degree K (-272.5 °C; -458.5 °F). The reason for this, according to the recent study, has to do with the gas cloud that extends from the central star to a distance of 21,000 AU (21 thousands times the distance between Earth and the Sun).
The gas cloud – which is the result of a jet that is being fired by the central star – is expanding at a rate that is about 10 times faster than what a single star could produce on its own. After conducting measurements with ALMA that revealed regions of the outflow that were never before seen (out to a distance of about 120,000 AUs), the team concluded that this is what is driving temperatures to levels lower than that of background radiation
They further argue that this was the result of the central star having collided with a binary companion in the past, and were even able to deduce what the primary was like before this took place. The primary, they claim, was a Red Giant Branch (RGB) or early-RGB star – i.e. a star in the final phase of its life cycle – whose expansion caused its binary companion to be pulled in by its gravity.
ALMA image of the Boomerang Nebula, showing its massive outflowCredit: ALMA (ESO/NAOJ/NRAO), R. Sahai
The companion star would have eventually merged with its core, which caused the outflow of gas to begin. As Raghvendra Sahai explained in a NRAO press release:
“These new data show us that most of the stellar envelope from the massive red giant star has been blasted out into space at speeds far beyond the capabilities of a single, red giant star. The only way to eject so much mass and at such extreme speeds is from the gravitational energy of two interacting stars, which would explain the puzzling properties of the ultra-cold outflow.”
These findings were made possible thanks to the ALMA’s ability to provide precise measurements on the extent, age, mass and kinetic energy of the nebula. Also, in addition to measuring the rate of outflow, they gathered that it has been taking place for around 1050 to 1925 years. The findings also indicate that the Boomerang Nebula’s days as the coldest object in the known Universe may be numbered.
Looking forward, the red giant star in the center is expected to continue the process of becoming a planetary nebula – where stars shed their outer layers to form an expanding shell of gas. In this respect, it is expected to shrink and get hotter, which will warm up the nebula around it and make it brighter.
As Lars-Åke Nyman, an astronomer at the Joint ALMA Observatory in Santiago, Chile, and co-author on the paper, said:
“We see this remarkable object at a very special, very short-lived period of its life. It’s possible these super cosmic freezers are quite common in the universe, but they can only maintain such extreme temperatures for a relatively short time.”
These findings could also provide new insights into another cosmological mystery, which is how giant stars and their companions behave. When the larger star in these systems exists its main-sequence phase, it may consume its smaller companion and similarly become a “cosmic freezer”. Herein lies the value of objects like the Boomerang Nebula, which challenges conventional ideas about the interactions of binary systems.
It also demonstrates the value of next-generations instruments like ALMA. Given their superior optical capabilities and ability to obtain more high-resolution information, they can show us some never-before-seen things about our Universe, which can only challenge our preconceived notions of what is possible out there.
Beyond the Solar System’s Main Asteroid Belt lies the realm of the giants. It is here, staring with Jupiter and extending to Neptune, that the largest planets in the Solar System are located. Appropriately named “gas giants” because of their composition, these planets dwarf the rocky (terrestrial) planets of the inner Solar System many times over.
Just take a look at Saturn, the gas giant that takes its name from the Roman god of agriculture, and the second largest planet in the Solar System (behind Jupiter). In addition to its beautiful ring system and its large system of moons, this planet is renowned for its incredible size. Just how big is this planet? Well that depends on what your frame of reference is.
Diameter:
First let’s consider how large Saturn is from one end to the other – i.e. it’s diameter. The equatorial diameter of Saturn is 120,536 km ± 8 km (74,898 ± 5 mi) – or the equivalent of almost 9.5 Earths. However, as with all planets, their is a difference between the equatorial vs. the polar diameter. This difference is due to the flattening the planet experiences at the poles, which is caused by the planet’s rapid rotation.
Like all the giant planets, Saturn is many times the size of Earth and the other rocky planets. Credit: NASA/JPL-Caltech/Space Science Institute.
The poles are about 5,904 km closer to the center of Saturn than points on the equator. As a result, Saturn’s polar radius is about 108,728 ± 20 km (67,560 ± 12 mi) – or the equivalent of 8.5 Earths. That’s a pretty big difference, and you can actually see that Saturn looks a little squashed in pictures. Just for comparison, the equatorial diameter of Saturn is 9.4 times bigger than Earth, and it’s about 84% the diameter of Jupiter.
Volume and Surface Area:
In terms of volume and surface area, the numbers get even more impressive! For starters, the surface area of Saturn is 42.7 billion km² (16.5 billion sq miles), which works out to about 83.7 times the surface area of Earth. That’s smaller than Jupiter though, being only 68.7% of Jupiter’s surface area. Still, that is pretty astounding when put into perspective.
On the other hand, Saturn has a volume of 827.13 trillion km³ (198.44 trillion cubic miles), which effectively means you could fit Earth inside of it 763 times over and still have room enough for about twenty Moons! Again, Jupiter has it beat since Saturn has only 57.8% the volume of Jupiter. It’s big, but Jupiter is just that much bigger.
Mass and Density:
What about mass? Of course Saturn is much, much, MUCH more massive than Earth. In fact, it’s mass has been estimated to be a whopping 568,360,000 trillion trillion kg (1,253,000,000 trillion trillion lbs) – which works out to 95 times the mass of Earth. Granted, that only works out to about 30% the mass of Jupiter, but that’s still a staggering amount of matter.
Diagram of Saturn’s interior. Credit: Kelvinsong/Wikipedia Commons
Looking at the numbers, you may notice that this seems like a bit of a discrepancy. If you could actually fit 763 Earth-sized planets inside Saturn with room to spare, how is it that it is only 95 times Earth’s mass? The answer to that has to do with density. Since Saturn is a gas giant, its matter is distributed less densely than a rocky planet’s.
Whereas Earth has a density of 5.514 g/cm³ (or 0.1992 lb per cubic inch), Saturn’s density is only 0.687 g/cm3 (0.0248 lb/cu in). Like all gas giants, Saturn’s is made up largely of gases that exist under varying degrees of pressure. Whereas the density increases considerably the deeper one goes into Saturn’s interior, the overall density is less than that of water – 1 g/cm³ (0.0361273 lb/cu in).
Yes, Saturn is quite the behemoth. And yet, ongoing investigations into extra-solar planets are revealing that even it and its big brother Jupiter can be beaten in the size department. In fact, thanks to the Kepler mission and other exoplanet surveys, astronomers have found a plethora of “Super-Jupiters” in the cosmos, which refers to planets that are up to 80 times the mass of Jupiter.
I guess the takeaway from this is that there’s always a bigger planet out there. So watch your step and remember not to throw your weight (or mass or volume) around!
Pleiades stars. Image: NASA, ESA, AURA/Caltech, Palomar Observatory. Credit: D. Soderblom and E. Nelan (STScI), F. Benedict and B. Arthur (U. Texas), and B. Jones (Lick Obs.)
Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the universally-renowned cluster known for its seven major points of light – The Pleiades Cluster!
During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.
One of these is the famous Pleiades Cluster, also known as the Seven Sisters (and countless other names). An open star cluster located approximately 390 to 456 light years from Earth in the constellation of Taurus, this cluster is dominated by very bright, hot blue stars. Being both bright and of one of the nearest star clusters to Earth, this cluster is easily visible to the naked eye in the night sky.
Description:
The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygete, Celaeno, and Alcyone, along with their parents Atlas and Pleione. To the X-ray telescopes on board the orbiting ROSAT observatory, the cluster also presents an impressive, but slightly altered, appearance.
An optical image of the Pleiades. Credit: NOAO/AURA/NSF
This false color image was produced from ROSAT observations by translating different X-ray energy bands to visual colors – the lowest energies are shown in red, medium in green, and highest energies in blue. (The green boxes mark the position of the seven brightest visual stars.)
The Pleiades stars seen in X-rays have extremely hot, tenuous outer atmospheres called coronas and the range of colors corresponds to different coronal temperatures. This helps to determine mass and the presence of brown dwarf stars within Messier 45. As Greg Ushomirsky (et al) said in a 1998 study:
“We present an analytic calculation of the thermonuclear depletion of the light elements lithium, beryllium, and boron in fully convective, low-mass stars. Under the presumption that the pre-main-sequence star is always fully mixed during contraction, we find that the burning of these rare light elements can be computed analytically, even when the star is degenerate. Using the effective temperature as a free parameter, we constrain the properties of low-mass stars from observational data, independently of the uncertainties associated with modeling their atmospheres and convection. Our analytic solution explains the dependence of the age at a given level of elemental depletion on the stellar effective temperature, nuclear cross sections, and chemical composition. These results are also useful as benchmarks to those constructing full stellar models. Most importantly, our results allow observers to translate lithium nondetections in young cluster members into a model-independent minimum age for that cluster. Using this procedure, we have found lower limits to the ages of the Pleiades (100 Myr) and Alpha Persei (60 Myr) clusters. Dating an open cluster using low-mass stars is also independent of techniques that fit upper main-sequence evolution. Comparison of these methods provides crucial information on the amount of convective overshooting (or rotationally induced mixing) that occurs during core hydrogen burning in the 5-10 Mo stars typically at the main-sequence turnoff for these clusters.”
As one of the closest of star clusters to our solar system, M45 is dominated by hot blue stars that have only formed within the last 100 million years. Alongside Maia is a reflection nebula discovered by Tempel faint nebula which accompanies Merope was discovered by master observer E.E. Barnard. These were first believed to be left over from the formation of the cluster.
Messier 45. Credit: Boris Stromar
However, it didn’t take many years of observation of proper motion for astronomers to realize the Pleiades were actually moving through a cloud of interstellar dust. While this pleasing blue group is still only 440 light years away, it only has about another 250 million years left before tidal interactions will tear it apart. By then, its relative motion will have carried it from the constellation of Taurus to the southern portion of Orion!
Of course, many observers aren’t quite sure if they are seeing the nebulosity in M45 or not. Chances are, if you’re seeing what appears to be a “fog” around the bright stars – you’re on it. Only large aperture or photography reveals the full extent of the reflection nebula… and there’s a whole lot of scientific reasons for it. Said Steven Gibson (et al) in a 2003 study:
“The scattering geometry analysis is complicated by the blending of light from many stars and the likely presence of more than one scattering layer. Despite these complications, we conclude that most of the scattered light comes from dust in front of the stars in at least two scattering layers, one far in front and extensive, the other nearer the stars and confined to areas of heavy nebulosity. The first layer can be approximated as an optically thin, foreground slab whose line-of-sight separation from the stars averages ~0.7 pc. The second layer is also optically thin in most locations and may lie at less than half the separation of the first layer, perhaps with some material among or behind the stars. The association of nebulosity peripheral to the main condensation around the brightest stars is not clear. Models with standard grain properties cannot account for the faintness of the scattered UV light relative to the optical. Some combination of significant changes in grain model albedo and phase function asymmetry values is required. Our best-performing model has a UV albedo of 0.22+/-0.07 and a scattering asymmetry of 0.74+/-0.06. Hypothetical optically thick dust clumps missed by interstellar sight line measurements have little effect on the nebular colors but might shift the interpretation of our derived scattering properties from individual grains to the bulk medium.”
Since the Pleaides really is close to our solar system, have astronomers been able to detect anything within its boundaries that has surprised them? The answer is yes. according to a 1998 study by E.L. Martin:
“We present the discovery of an object in the Pleiades open cluster, named Teide 2, with optical and infrared photometry that places it on the cluster sequence slightly below the expected substellar mass limit. We have obtained low- and high-resolution spectra that allow us to determine its spectral type (M6), radial velocity, and rotational broadening and to detect H? in emission and Li I in absorption. All the observed properties strongly support the membership of Teide 2 in the Pleiades. This object has an important role in defining the reappearance of lithium below the substellar limit in the Pleiades.”
The M45 cluster. Credit: Wikipedia Commons/Did23
And what star is that? One cataloged as known as HD 23514, which has a mass and luminosity a bit greater than our Sun. But it’s a star surrounded by an extraordinary number of hot dust particles. “Unusually massive amounts of dust, as seen at the Pleiades and Aries stars, cannot be primordial but rather must be the second-generation debris generated by collisions of large objects,” said Song, “”Collisions between comets or asteroids wouldn’t produce anywhere near the amount of dust we are seeing.”
The astronomers analyzed emissions from countless microscopic dust particles and concluded that the most likely explanation is that the particles are debris from the violent collision of planets or planetary embryos. Song calls the dust particles the “building blocks of planets,” which can accumulate into comets and small asteroid-size bodies and then clump together to form planetary embryos, eventually becoming full-fledged planets.
“In the process of creating rocky, terrestrial planets, some objects collide and grow into planets, while others shatter into dust,” Song said. “We are seeing that dust.”
History of Observation:
The recognition of the Pleiades dates back to antiquity, and its stars are known by many names in many cultures. The Greeks and Romans referred to them as the “Starry Seven,” the “Net of Stars,” “The Seven Virgins,” “The Daughters of Pleione,” and even “The Children of Atlas.” The Egyptians referred to them as “The Stars of Athyr;” the Germans as “Siebengestiren” (the Seven Stars); the Russians as “Baba” after Baba Yaga – the witch who flew through the skies on her fiery broom.
The Pleiades by Elihu Vedder (1885). Credit: Metropolitan Museum of Art, New York City.
The Japanese call them “Subaru;” Norsemen saw them as packs of dogs; and the Tongans as “Matarii” (the Little Eyes). American Indians viewed the Pleiades as seven maidens placed high upon a tower to protect them from the claws of giant bears, and even Tolkien immortalized the star group in The Hobbit as “Remmirath.” The Pleiades were even mentioned in the Bible! So, you see, no matter where we look in our “starry” history, this cluster of seven bright stars has been part of it.
Charles Messier would log it on March 4, 1769 where his only comment would be: “Cluster of stars known by the name Pleiades: the position reported is that of the star Alcyone.” Even though historic astronomers did little more than comment on M45’s presence, we’re still glad the Charles logged it – for it never received another “official” catalog designation!
Locating Messier 45:
Most normally the Pleiades are easily found with the unaided eye as a very visible cluster of stars about a hand span northwest of Orion. However, if sky conditions are bright, M45 might be a little more difficult to spot. If so, look for bright, red star Aldebaran and set your sights about 10 degrees (an average fist width) northwest.
It will show very easily in any size optics and under virtually any conditions – except for clouds and daylight! Messier 45’s large size makes it an ideal candidate for binoculars, where it will cover about half the average field of view. When using a telescope, chose the least amount of magnification possible to see the entire cluster and use higher magnification to study individual stars.
The location of the Centaurus constellation in the southern sky. Credit: IAU/Sky & Telescope magazine/Roger Sinnott & Rick Fienberg
And as always, here are the quick facts on this Messier Object to help you get started:
Object Name: Messier 45 Alternative Designations: M45, the Pleiades, Seven Sisters, Subaru Object Type: Open Galactic Star Cluster, Reflection Nebula Constellation: Taurus Right Ascension: 03 : 47.0 (h:m) Declination: +24 : 07 (deg:m) Distance: 0.44 (kly) Visual Brightness: 1.6 (mag) Apparent Dimension: 110.0 (arc min)
The NICER payload, shown here on the outside of the International Space Station. Credit: NASA
When a large star undergoes gravitational collapse near the end of its lifespan, a neutron star is often the result. This is what remains after the outer layers of the star have been blown off in a massive explosion (i.e. a supernova) and the core has compressed to extreme density. Afterwards, the star’s rotation rate increases considerably, and where they emit beams of electromagnetic radiation, they become “pulsars”.
And now, 50 years after they were first discovered by British astrophysicist Jocelyn Bell, the first mission devoted to the study of these objects is about to be mounted. It is known as the Neutron Star Interior Composition Explorer (NICER), a two-part experiment that will be deployed to the International Space Station this summer. If all goes well, this platform will shed light on one of the greatest astronomical mysteries, and test out new technologies.
Astronomers have been studying neutron stars for almost a century, which have yielded some very precise measurements of their masses and radii. However, what actually transpires in the interior of a neutron star remains an enduring mystery. While numerous models have been advanced that describe the physics governing their interiors, it is still unclear how matter would behave under these types of conditions.
Not surprising, since neutron stars typically hold about 1.4 times the mass of our Sun (or 460,000 times the mass of the Earth) within a volume of space that is the size of a city. This kind of situation, where a considerable amount of matter is packed into a very small volume – resulting in crushing gravity and an incredible matter density – is not seen anywhere else in the Universe.
As Keith Gendreau, a scientist at NASA’s Goddard Space Flight Center, explained in a recent NASA press statement:
“The nature of matter under these conditions is a decades-old unsolved problem. Theory has advanced a host of models to describe the physics governing the interiors of neutron stars. With NICER, we can finally test these theories with precise observations.”
NICE was developed by NASA’s Goddard Space Flight Center with the assistance of the Massachusetts Institute of Technology (MIT), the Naval Research Laboratory, and universities across the U.S. and Canada. It consists of a refrigerator-sized apparatus that contains 56 X-ray telescopes and silicon detectors. Though it was originally intended to be deployed late in 2016, a launch window did not become available until this year.
Once installed as an external payload aboard the ISS, it will gather data on neutron stars (mainly pulsars) over an 18-month period by observing neutron stars in the X-ray band. Even though these stars emit radiation across the spectrum, X-ray observations are believed to be the most promising when it comes to revealing things about their structure and various high-energy phenomena associated with them.
SEXTANT will demonstrate a GPS-like absolute position determination capability by observing millisecond pulsars. Credit: NASA
These include starquakes, thermonuclear explosions, and the most powerful magnetic fields known in the Universe. To do this, NICER will collect X-rays generated from these stars’ magnetic fields and magnetic poles. This is key, since it is at the poles that the strength of a neutron star’s magnetic fields causes particles to be trapped and rain down on the surface, which produces X-rays.
In pulsars, it is these intense magnetic fields which cause energetic particles to become focused beams of radiation. These beams are what give pulsars their name, as they appear like flashes thanks to the star’s rotation (giving them their “lighthouse”-like appearance). As physicists have observed, these pulsations are predictable, and can therefore be used the same way atomic-clocks and Global Positioning System are here on Earth.
While the primary goal of NICER is science, it also offers the possibility of testing new forms of technology. For instance, the instrument will be used to conduct the first-ever demonstration of autonomous X-ray pulsar-based navigation. As part of the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), the team will use NICER’s telescopes to detect the X-ray beams generated by pulsars to estimate the arrival times of their pulses.
The team will then use specifically-designed algorithms to create an on-board navigation solution. In the future, interstellar spaceships could theoretically rely on this to calculate their location autonomously. This wold allow them to find their way in space without having to rely on NASA’s Deep Space Network (DSN), which is considered to be the most sensitive telecommunications system in the world.
Beyond navigation, the NICER project also hopes to conduct the first-ever test of the viability of X-ray based-communications (XCOM). By using X-rays to send and receive data (in the same way we currently use radio waves), spacecraft could transmit data at the rate of gigabits per second over interplanetary distances. Such a capacity could revolutionize the way we communicate with crewed missions, rover and orbiters.
Central to both demonstrations is the Modulated X-ray Source (MXS), which the NICER team developed to calibrate the payload’s detectors and test the navigation algorithms. Generating X-rays with rapidly varying intensity (by switching on and off many times per second), this device will simulate a neutron star’s pulsations. As Gendreau explained:
“This is a very interesting experiment that we’re doing on the space station. We’ve had a lot of great support from the science and space technology folks at NASA Headquarters. They have helped us advance the technologies that make NICER possible as well as those that NICER will demonstrate. The mission is blazing trails on several different levels.”
It is hoped that the MXS will be ready to ship to the station sometime next year; at which time, navigation and communication demonstrations could begin. And it is expected that before July 25th, which will mark the 50th anniversary of Bell’s discovery, the team will have collected enough data to present findings at scientific conferences scheduled for later this year.
If successful, NICER could revolutionize our understanding of how neutron stars (and how matter behaves in a super-dense state) behaves. This knowledge could also help us to understand other cosmological mysteries such as black holes. On top of that, X-ray communications and navigation could revolutionize space exploration and travel as we know it. In addition to providing greater returns from robotic missions located closer to home, it could also enable more lucrative missions to locations in the outer Solar System and even beyond.
Artist's impression of merging binary black holes. Credit: LIGO/A. Simonnet.
A third gravitational wave has been detected by the Laser Interferometer Gravitational-wave Observatory (LIGO). An international team announced the detection today, while the event itself was detected on January 4th, 2017. Gravitational waves are ripples in space-time predicted by Albert Einstein over a century ago.
LIGO consists of two facilities: one in Hanford, Washington and one in Livingston, Louisiana. When LIGO announced its first gravitational wave back in February 2016 (detected in September 2015), it opened up a new window into astronomy. With this gravitational wave, the third one detected, that new window is getting larger. So far, all three waves detected have been created by the merging of black holes.
When the first gravitational wave was finally detected, over a hundred years after Einstein predicted it, it helped confirm Einstein’s description of space-time as an integrated continuum. It’s often said that it’s not a good idea to bet against Einstein, and this third detection just strengthens Einstein’s theory.
Like the previous two detections, this one was created by the merging of two black holes. These two were different sizes from each other; one was about 31.2 solar masses, and the other was about 19.4 solar masses. The combined 50 solar mass event caused the third wave, which is named GW170104. The black holes were about 3 billion light years away.
LIGO is showing us that their is a population of binary black holes out there. “Our handful of detections so far is revealing an intriguing black hole population we did not know existed until now,” said Northwestern’s Vicky Kalogera, a senior astrophysicist with the LIGO Scientific Collaboration (LSC), which conducts research related to the twin LIGO detectors, located in the U.S.
“Now we have three pairs of black holes, each pair ending their death spiral dance over millions or billions of years in some of the most powerful explosions in the universe. In astronomy, we say with three objects of the same type you have a class. We have a population, and we can do analysis.”
The Laser Interferometer Gravitational-Wave Observatory (LIGO)facility in Livingston, Louisiana. The other facility is located in Hanford, Washington. Image: LIGO
When we say that gravitational waves have opened up a new window on astronomy, that window opens onto black holes themselves. Beyond confirming Einstein’s predictions, and establishing a population of binary black holes, LIGO can characterize and measure those black holes. We can learn the holes’ masses and their spin characteristics.
“Once again, the black holes are heavy,“ said Shane Larson, of Northwestern University and Adler Planetarium in Chicago. “The first black holes LIGO detected were twice as heavy as we ever would have expected. Now we’ve all been churning our cranks trying to figure out all the interesting myriad ways we can imagine the universe making big and heavy black holes. And Northwestern is strong in this research area, so we are excited.”
This third finding strengthens the case for the existence of a new class of black holes: binary black holes that are locked in relationship with each other. It also shows that these objects can be larger than thought before LIGO detected them.
“It is remarkable that humans can put together a story and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us.” – David Shoemaker, MIT
“We have further confirmation of the existence of black holes that are heavier than 20 solar masses, objects we didn’t know existed before LIGO detected them,” said David Shoemaker of MIT, spokesperson for the LIGO Scientific Collaboration . “It is remarkable that humans can put together a story and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us.”
An artist’s impression of two merging black holes. Image: NASA/CXC/A. Hobart
“With the third confirmed detection of gravitational waves from the collision of two black holes, LIGO is establishing itself as a powerful observatory for revealing the dark side of the universe,” said David Reitze of Caltech, executive director of the LIGO Laboratory and a Northwestern alumnus. “While LIGO is uniquely suited to observing these types of events, we hope to see other types of astrophysical events soon, such as the violent collision of two neutron stars.”
A tell-tale chirping sound confirms the detection of a gravitational wave, and you can hear it described and explained here, on a Northwestern University podcast.
This artist's impression shows a star crossing the event horizon of a supermassive black hole located in the center of a galaxy. The black hole is so large and massive that tidal effects on the star are negligible, and the star is swallowed whole. Image: Mark A. Garlick/CfA
At the center of our Milky Way galaxy dwells a behemoth. An object so massive that nothing can escape its gravitational pull, not even light. In fact, we think most galaxies have one of them. They are, of course, supermassive black holes.
Supermassive black holes are stars that have collapsed into a singularity. Einstein’s General Theory of Relativity predicted their existence. And these black holes are surrounded by what’s known as an event horizon, which is kind of like the point of no return for anything getting too close to the black hole. But nobody has actually proven the existence of the event horizon yet.
Some theorists think that something else might lie at the center of galaxies, a supermassive object event stranger than a supermassive black hole. Theorists think these objects have somehow avoided a black hole’s fate, and have not collapsed into a singularity. They would have no event horizon, and would have a solid surface instead.
“Our whole point here is to turn this idea of an event horizon into an experimental science, and find out if event horizons really do exist or not,” – Pawan Kumar Professor of Astrophysics, University of Texas at Austin.
A team of researchers at the University of Texas at Austin and Harvard University have tackled the problem. Wenbin Lu, Pawan Kumar, and Ramesh Narayan wanted to shed some light onto the event horizon problem. They wondered about the solid surface object, and what would happen when an object like a star collided with it. They published their results in the Monthly Notices of the Royal Astronomical Society.
Artist’s conception of the event horizon of a black hole. Credit: Victor de Schwanberg/Science Photo Library
“Our whole point here is to turn this idea of an event horizon into an experimental science, and find out if event horizons really do exist or not,” said Pawan Kumar, Professor of Astrophysics at The University of Texas at Austin, in a press release.
Since a black hole is a star collapsed into a singularity, it has no surface area, and instead has an event horizon. But if the other theory turns out to be true, and the object has a solid surface instead of an event horizon, then any object colliding with it would be destroyed. If a star was to collide with this hard surface and be destroyed, the team surmised, then the gas from the star would enshroud the object and shine brightly for months, or even years.
This is the first in a sequence of two artist’s impressions that shows a huge, massive sphere in the center of a galaxy, rather than a supermassive black hole. Here a star moves towards and then smashes into the hard surface of the sphere, flinging out debris. The impact heats up the site of the collision. Image: Mark A. Garlick/CfAIn this second artist’s impression a huge sphere in the center of a galaxy is shown after a star has collided with it. Enormous amounts of heat and a dramatic increase in the brightness of the sphere are generated by this event. The lack of observation of such flares from the center of galaxies means that this hypothetical scenario is almost completely ruled out. Image: Mark A. Garlick/CfA
If that were the case, then the team knew what to look for. They also worked out how often this would happen.
“We estimated the rate of stars falling onto supermassive black holes,” Lu said in the same press release. “Nearly every galaxy has one. We only considered the most massive ones, which weigh about 100 million solar masses or more. There are about a million of them within a few billion light-years of Earth.”
Now they needed a way to search the sky for these objects, and they found it in the archives of the Pan-STARRS telescope. Pan-STARRS is a 1.8 meter telescope in Hawaii. That telescope recently completed a survey of half of the northern hemisphere of the sky. In that survey, Pan-STAARS spent 3.5 years looking for transient objects in the sky, objects that brighten and then fade. They searched the Pan-STARR archives for transient objects that had the signature they predicted from stars colliding with these supermassive, hard-surfaced objects.
The trio predicted that in the 3.5 year time-frame captured by the Pan-STAARS survey, 10 of these collisions would occur and should be represented in the data.
“It turns out it should have detected more than 10 of them, if the hard-surface theory is true.” – Wenbin Lu, Dept. of Astronomy, University of Texas at Austin.
“Given the rate of stars falling onto black holes and the number density of black holes in the nearby universe, we calculated how many such transients Pan-STARRS should have detected over a period of operation of 3.5 years. It turns out it should have detected more than 10 of them, if the hard-surface theory is true,” Lu said.
The team found none of the flare-ups they expected to see if the hard-surface theory is true.
“Our work implies that some, and perhaps all, black holes have event horizons…” – Ramesh Narayan, Harvard-Smithsonian Center for Astrophysics.
What might seem like a failure, isn’t one of course. Not for Einstein, anyway. This represents yet another successful test of Einstein’s Theory of General Relativity, showing that the event horizon predicted in his theory does seem to exist.
As for the team, they haven’t abandoned the idea yet. In fact, according to Pawan Kumar, Professor of Astrophysics, University of Texas at Austin, “Our motive is not so much to establish that there is a hard surface, but to push the boundary of knowledge and find concrete evidence that really, there is an event horizon around black holes.”
“General Relativity has passed another critical test.” – Ramesh Narayan, Harvard-Smithsonian Center for Astrophysics.
“Our work implies that some, and perhaps all, black holes have event horizons and that material really does disappear from the observable universe when pulled into these exotic objects, as we’ve expected for decades,” Narayan said. “General Relativity has passed another critical test.”
The team plans to continue to look for the flare-ups associated with the hard-surface theory. Their look into the Pan-STARRS data was just their first crack at it.
An artist’s illustration of the Large Synoptic Survey Telescope with a simulated night sky. The team hopes to use the LSST to further refine their search for hard-surface supermassive objects. Image: Todd Mason, Mason Productions Inc. / LSST Corporation
They’re hoping to improve their test with the upcoming Large Synoptic Survey Telescope (LSST) being built in Chile. The LSST is a wide field telescope that will capture images of the night sky every 20 seconds over a ten-year span. Every few nights, the LSST will give us an image of the entire available night sky. This will make the study of transient objects much easier and effective.
The surface of Venus has been a mystery to scientists ever since the Space Age began. Thanks to its dense atmosphere, its surface is inaccessible to direct observations. In terms of exploration, the only missions to penetrate the atmosphere or reach the surface were only able to transmit data back for a matter of hours. And what we have managed to learn over the years has served to deepen its mysteries as well.
For instance, for years, scientists have been aware of the fact that Venus experiences volcanic activity similar to Earth (as evidenced by lighting storms in its atmosphere), but very few volcanoes have been detected on its surface. But thanks to a new study from the School of Earth and Environmental Sciences (SEES) at the University of St. Andrews, we may be ready to put that particular mystery to bed.
The study was conducted by Dr. Sami Mikhail, a lecturer with the SEES, with the assistance of researchers from the University of Strasbourg. In examining Venus’ geological past, Mikhail and his colleagues sought to understand how it is that the most Earth-like planet in our Solar System could be considerably less geologically-active than Earth. According to their findings, the answer lies in the nature of Venus’ crust, which has a much higher plasticity.
Image of the “pancake volcanoes” located in the Eistla region, taken by the Magellan space probe. Credit: NASA/JPL
This is due to the intense heat on Venus’ surface, which averages at 737 K (462 °C; 864 °F) with very little variation between day and night or over the course of a year. Given that this heat is enough to melt lead, it has the effect of keeping Venus’ silicate crust in a softened and semi-viscous state. This prevents lava magmas from being able to move through cracks in the planets’ crust and form volcanoes (as they do on Earth).
In fact, since the crust is not particularly solid, cracks are unable to form in the crust at all, which causes magma to get stuck in the soft, malleable crust. This is also what prevents Venus from experiencing tectonic activity similar to what Earth experiences, where plates drift across the surface and collide, occasionally forcing magma up through vents. This cycle, it should be noted, is crucial to Earth’s carbon cycle and plays a vital role in Earth’s climate.
Not only do these findings explain one of the larger mysteries about Venus’ geological past, but they also are an important step towards differentiating between Earth and it’s “sister planet”. The implications of this goes far beyond the Solar System. As Dr. Mikhail said in a St. Andrews University press release:
“If we can understand how and why two, almost identical, planets became so very different, then we as geologists, can inform astronomers how humanity could find other habitable Earth-like planets, and avoid uninhabitable Earth-like planets that turn out to be more Venus-like which is a barren, hot, and hellish wasteland.”
Volcanoes and lava flows on Venus. Credit: NASA/JPL
In terms of size, composition, structure, chemistry, and its position within the Solar System (i.e. within the Sun’s habitable zone), Venus is the most-Earth like planet discovered to date. And yet, the fact that it is slightly closer to our Sun has resulted in it having a vastly different atmosphere and geological history. And these differences are what make it the hellish, uninhabitable place that is today.
Beyond our Solar System, astronomers have discovered thousands of exoplanets orbiting various types of stars. In some cases, where the planets exist close to their sun and are in possession of an atmosphere, the planets have been designated as being “Venus-like“. This naturally sets them apart from the planets that are of particular interest to exoplanet hunters – i.e. the “Earth-like” ones.
Knowing how and why these two very similar planets can differ so dramatically in terms of their geological and environmental conditions is therefore key to being able to tell the difference between planets that are conducive to life and hostile to life. That can only come in handy when we begin to study multiple-planet systems (such as the seven-planet system of TRAPPIST-1) more closely.
